Windows NT类的操作系统，也就是Windows NT/2000/XP中，有一个特殊文件，也就是“BOOT.INI”文件，这个文件会很轻松地按照我们的需求设置好多重启动系统。

“BOOT.INI”文件会在已经安装了 Windows NT/2000/XP/2003 的操作系统的所在分区，一般默认为C:\下面存在。但是它默认具有隐藏和系统属性，所以你要设置你的文件夹选项，以便把“BOOT.INI”文件显示出来。我们可以用任何一种文本编辑器来打开他它。一般情况下，它的内容如下:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\Windows
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\Windows="Microsoft Windows XP Professional" /fastdetect

在Windows 2000或者是XP系统中，我们可以很容易的设置“BOOT.INI”文件。那就是在“我的电脑”上面点击右键，选择“属性”打开“系统属性”对话框，再点击“高级”选项卡，在“启动和故障修复”里面点击“设置”按钮，就可以打开“启动和故障修复”对话框了，在这里面我们就可以对它进行详细设置。

如果你拥有Windows XP操作系统，那么你可以用“系统配置实用程序”来更方便的编辑“BOOT.INI”文件。具体做法是:打开“开始”菜单，点击“运行”命令，再在弹出的文本框中输入“Msconfig”点击“确定”后就会弹出“系统配置实用程序”，再点击“BOOT.INI”选项卡，就会出现如图所示的界面。在这里，我们可以很方便地设置文件。

言归正传，现在，来说明一下这个文件内容的含义。

1.系统加载部分（[boot loader]）

这一部分很简单，只有两个设定。那就是“timeout=”和“default=”。
“timeout=”就是设定开机时系统引导菜单显示的时间，超过设定值则自动加载下面“default=”指定的操作系统。默认值是30，单位为秒。我们可以在这里面设定等待时间的长短。如果将其设为“0”那么就是不显示系统引导菜单。
“default=”则是设定默认引导的操作系统。而等号后面的操作系统必须是已经在“[operating systems]”中存在的。如果想默认为加载另外的操作系统，我们可以参看“[operating systems]”中的操作系统列表，然后把想要加载的操作系统按照格式写到“default=”后面就可以了。


2.操作系统部分（[operating systems]）

在这里面，列出了机器上所安装的全部操作系统。比如机器上只有一个操作系统，那么就只有一条信息，那就是“multi(0)disk(0)rdisk(0)partition(1)\Windows="Microsoft Windows XP Professional" /fastdetect”
在这里需要注意的是，在英文引号内的文字就是引导操作系统菜单时显示出来的让我们选择操作系统的提示文字，在这里面我们可以随意更改。而“multi(0)disk(0)rdisk(0)partition(1) \Windows”这一句就需要些解释了。因为它涉及ARC（高级RISC计算机）命名，它是x86或RISC计算机中用于标识设备的动态方法。

ARC命名的第一部分用于标识硬件适配卡/磁盘控制器，它有两个选项:SCSI和Multi。

Multi表示一个非SCSI硬盘或一个由SCSI BIOS访问的SCSI硬盘，而SCSI则表示一个SCSI BIOS禁止的SCSI硬盘。(x)是硬件适配卡序号。Disk(x)表示SCSI总线号。如果硬件适配卡为Multi，其正确表示方法就为disk(0)，rdisk(x)则表示硬盘的序号，如果硬件适配卡为SCSI则忽略此值;
partition(x)表示硬盘的分区序号。了解这些，我们就可以解释前面那条信息的含义了，即“multi(0)disk(0)rdisk(0)partition(1) \Windows”为，在0号非SCSI设备上的第0号磁盘上的第一个分区里面的“Windows”目录下可以找到能够启动的操作系统。
等号后的内容前面已经说过，那个就是引导菜单显示出来的供我们选择的提示文字。而后面的“/fastdetect”又是作什么用的呢？这是一个开关符，用来控制启动该操作系统时的具体选项，下面再来详细的介绍各种开关符的含义:

/3GB:这是Win2000 SP3新引入的。这使得用户区和系统区分为3G比1G的比例。只有用户使用NT企业版，应用程序也支持3GB选项时，此选项才生效。

/BASEVIDE使用标准VGA方式启动。这种方式主要用于显示驱动程序失效时。

/BAUDRATE:指出用于调度的波特率，如果用户不设置，则使用默认的9600，而对于线缆Modem则使用19200。

/BOOTLOG:使Win2000将日志写入 %SystemRoot%\NTBTLOG.TXT 。

/BURNMEMORY=:使NT在已知的内存上少使用指定的数量，如果/burnmemory=64，则有64M内存NT不使用。

/CRASHDEBUG:调度器在NT启动时启动，只有在内核错误时才有用，如果系统经常会无故出错，这个选项就很有用了。

/DEBUG:在启动NT时调入调度器，它可以在任何时间激活，在错误可以再次出现时使用它比较合适。

/DEBUGPORT= comx :指定用于调度的端口，其它X就指端口号。

/FASTDETECT:对于Win2000启动时，它使系统不检查串行口和并行口。

/HAL=<hal>:允许用户不使用默认的HAL。

/INTAFFINITY:设置多处理器HAL(HALMPS.DLL)，使编号最大的处理器接收中断请求。如果不设置此选项，Win2000会使所有处理器接收中断请求。

/KERNEL=<kernel>:与上面的功能相同，不过是针对SMP中的内核而言的。

/MAXMEM:n:指定NT可以使用的最大内存数，如果一个内存片损坏，这个开关就十分有用了。

/NODEBUG:不使用调试信息。

/NOGUIBOOT:指定此选项会使Win2000不加载VGA驱动程序，也就不会显示启动过程和失败时的兰屏信息。

/NOSERIALMICE=[COMx | COMx,y,z…]:在特定的COM中上禁止对串行鼠标的检测。如果用户有一个非鼠标设备接在COM口上，这个选项会十分有用。如果此开关未加参数，系统会禁止所有COM口。

/NUMPROC=n:只允许前N个系统处理器工作。

/ONECPU:在多处理器中只使用一个处理器。

/PCILOCK:不让NT为PCI设置分配IO/IRQ资源，而启用BIOS设置。

/SAFEBOOT:安全启动，这个大家一定十分熟悉，Win2000只启动HKLM\System\CurrentControlSet\Control\SafeBoot中的驱动程序和服务，其后跟三个参数MINIMAL，NETWORK或DSREPAIR之一。MINIMAL和NETWORK在允许网络下启动系统。而DSREPAIR要求系统从备份设备中调入活动目录的设置。还有一个选项是"(ALTERNATESHELL)"，它让系统调入由HKLM\System\CurrentControlSet\
SafeBoot\AlternateShell指定的SHELL程序，而不使用默认的Explorer。

/SOS:在调入驱动程序名时显示它的名字，在因驱动问题而无法启动时使用比较好。

/WIN95:在装有三个系统DOS、Win9x和Windows NT的系统上，让NTLDR直接调用Win9x。启动文件BOOTSECT.W40。

/WIN95DOS:在装有三个系统DOS、Win9x和Windows NT的系统上，让NTLDR直接调用DOS启动文件BOOTSECT.DOS

/YEAR=:使用指定的年份，如果设置为/YEAR=2005，那现在的时间就是2005年，此选项仅对NT4+SP4和Win2000生效。



补充:
/usepmtimer : 在win2k/2003/xp上，使用 QueryPerformanceCounter 函数可能执行得不好，导致这个问题的因为是 bios 中开启了AMD CPU 的 cool'n quiet 技术，解决的办法是在 boot.ini 中增加 /usepmtimer 参数
详细看这里: http://support.microsoft.com/kb/895980/zh-cn

更详细的英文说明

Boot INI Options Reference
Mark Russinovich

Published: November 1, 2006
Introduction

There are number of BOOT.INI switches that are useful for driver developers that wish to test their drivers under a variety of different system configurations without having to have a separate machine for every one. For example, limiting the amount of memory NT sees can be useful for stressing memory loads, and limiting the number of processors for testing scalability. I've compiled a complete list of the options that BOOT.INI currently supports. This list is reproduced in the Startup, Shutdown and Crashes chapter of Windows Internals, where you'll find more information about the boot process.

Note: to see what options a system has booted with examine HKLM\System\CurrentControlSet\Control\SystemStartOptions.

/3GB
Increases the size of the user process address space from 2 GB to 3 GB (and therefore reduces the size of system space from 2 GB to 1 GB). Giving virtual-memory- intensive applications such as database servers a larger address space can improve their performance. For an application to take advantage of this feature, however, two additional conditions must be met: the system must be running Windows XP, Windows Server 2003, Windows NT 4 Enterprise Edition, Windows 2000 Advanced Server or Datacenter Server and the application .exe must be flagged as a 3-GB-aware application. Applies to 32-bit systems only.

/BASEVIDEO
Causes Windows to use the standard VGA display driver for GUI-mode operations.

/BAUDRATE=
Enables kernel-mode debugging and specifies an override for the default baud rate (19200) at which a remote kernel debugger host will connect. Example: /BAUDRATE=115200.

/BOOTLOG
Causes Windows to write a log of the boot to the file %SystemRoot%\Ntbtlog.txt.

/BOOTLOGO
Use this switch to have Windows XP or Windows Server 2003 display an installable splash screen instead of the standard splash screen. First, create a 16-color (any 16 colors) 640x480 bitmap and save it in the Windows directory with the name Boot.bmp. Then add "/bootlogo /noguiboot" to the boot.ini selection.

/BREAK
Causes the hardware abstraction layer (HAL) to stop at a breakpoint at HAL initialization. The first thing the Windows kernel does when it initializes is to initialize the HAL, so this breakpoint is the earliest one possible. The HAL will wait indefinitely at the breakpoint until a kernel-debugger connection is made. If the switch is used without the /DEBUG switch, the system will Blue Screen with a STOP code of 0x00000078 (PHASE0_ EXCEPTION).

/BURNMEMORY=
Specifies an amount of memory Windows can't use (similar to the /MAXMEM switch). The value is specified in megabytes. Example: /BURNMEMORY=128 would indicate that Windows can't use 128 MB of the total physical memory on the machine.

/CHANNEL=
Used on conjunction with /DEBUGPORT=1394 to specify the IEEE 1394 channel through which kernel debugging communications will flow. This can be any number between 0 and 62 and defaults to 0 if not set.

/CLKLVL
Causes the standard x86 multiprocessor HAL (Halmps.dll) to configure itself for a level-sensitive system clock rather then an edge-triggered clock. Level-sensitive and edge-triggered are terms used to describe hardware interrupt types.

/CMDCONS
Passed when booting with into the Recovery Console (described later in this chapter).

/CRASHDEBUG
Causes the kernel debugger to be loaded when the system boots, but to remain inactive unless a crash occurs. This allows the serial port that the kernel debugger would use to be available for use by the system until the system crashes (vs. /DEBUG, which causes the kernel debugger to use the serial port for the life of the system session).

/DEBUG
Enables kernel-mode debugging.

/DEBUGPORT=
Enables kernel-mode debugging and specifies an override for the default serial (usually COM2 on systems with at least two serial ports) to which a remote kernel-debugger host is connected. Windows XP and Windows Server 2003 also support debugging through accept IEEE 1394 ports. Examples: /DEBUGPORT=COM2, /DEBUGPORT=1394.

/EXECUTE
This option disables no-execute protection. See the /NOEXECUTE switch for more information.

/FASTDETECT
Default boot option for Windows. Replaces the Windows NT 4 switch /NOSERIALMICE. The reason the qualifier exists (vs. just having NTDETECT perform this operation by default) is so that NTDETECT can support booting Windows NT 4. Windows Plug and Play device drivers perform detection of parallel and serial devices, but Windows NT 4 expects NTDETECT to perform the detection. Thus, specifying /FASTDETECT causes NTDETECT to skip parallel and serial device enumeration (actions that are not required when booting Windows), whereas omitting the switch causes NTDETECT to perform this enumeration (which is required for booting Windows NT 4).

/INTAFFINITY
Directs the standard x86 multiprocessor HAL (Halmps.dll) to set interrupt affinities such that only the highest numbered processor will receive interrupts. Without the switch, the HAL defaults to its normal behavior of letting all processors receive interrupts.

/KERNEL=/HAL=
Enable you to override Ntldr's default filename for the kernel image (Ntoskrnl.exe) and/or the HAL (Hal.dll). These options are useful for alternating between a checked kernel environment and a free (retail) kernel environment or even to manually select a different HAL. If you want to boot a checked environment that consists solely of the checked kernel and HAL, which is typically all that is needed to test drivers, follow these steps on a system installed with the free build:
Copy the checked versions of the kernel images from the checked build CD to your \Windows\System32 directory, giving the images different names than the default. For example, if you're on a uniprocessor, copy Ntoskrnl.exe to Ntoschk.exe and Ntkrnlpa.exe to Ntoschkpa.exe. If you're on a multiprocessor, copy Ntkrnlmp.exe to Ntoschk.exe and Ntkrpamp.exe to Ntoschkpa.exe. The kernel filename must be an 8.3-style short name.
Copy the checked version of the appropriate HAL needed for your system from \I386\Driver.cab on the checked build CD to your \Windows\System32 directory, naming it Halchk.dll. To determine which HAL to copy, open \Windows\Repair\Setup.log and search for Hal.dll; you'll find a line like \WINDOWS\system32\ hal.dll="halacpi.dll","1d8a1". The name immediately to the right of the equals sign is the name of the HAL you should copy. The HAL filename must be an 8.3-style short name.
Make a copy of the default line in the system's Boot.ini file.
In the string description of the boot selection, add something that indicates that the new selection will be for a checked build environment (for example, "Windows XP Professional Checked").
Add the following to the end of the new selection's line: /KERNEL=NTOSCHK.EXE /HAL= HALCHK.DLL
Now when the selection menu appears during the boot process you can select the new entry to boot a checked environment or select the entry you were using to boot the free build.

/LASTKNOWNGOOD
Causes the system to boot as if the LastKnownGood boot option was selected.

/MAXMEM=
Limits Windows to ignore (not use) physical memory beyond the amount indicated. The number is interpreted in megabytes. Example: /MAXMEM=32 would limit the system to using the first 32 MB of physical memory even if more were present.

/MAXPROCSPERCLUSTER=
For the standard x86 multiprocessor HAL (Halmps.dll), forces cluster-mode Advanced Programmable Interrupt Controller (APIC) addressing (not supported on systems with an 82489DX external APIC interrupt controller).

/MININT
This option is used by Windows PE (Preinstallation Environment) and causes the Configuration Manager to load the Registry SYSTEM hive as a volatile hive such that changes made to it in memory are not saved back to the hive image.

/NODEBUG
Prevents kernel-mode debugging from being initialized. Overrides the specification of any of the three debug-related switches, /DEBUG, /DEBUGPORT, and /BAUDRATE.

/NOEXECUTE
This option is only available on 32-bit versions of Windows when running on processors supporting no-execute protection. It enables no-execute protection (also known as Data Execution Protection - DEP), which results in the Memory Manager marking pages containing data as no-execute so that they cannot be executed as code. This can be useful for preventing malicious code from exploiting buffer overflow bugs with unexpected program input in order to execute arbitrary code. No-execute protection is always enabled on 64-bit versions of Windows on processors that support no-execute protection. There are several options you can specify with this switch:
/NOEXECUTE=OPTIN Enables DEP for core system images and those specified in the DEP configuration dialog.
/NOEXECUTE=OPTOUT Enables DEP for all images except those specified in the DEP configuration dialog.
/NOEXECUTE=ALWAYSON Enables DEP on all images.
/NOEXECUTE=ALWAYSOFF Disables DEP.

/NOGUIBOOT
Instructs Windows not to initialize the VGA video driver responsible for presenting bitmapped graphics during the boot process. The driver is used to display boot progress information, so disabling it will disable the ability of Windows to show this information.

/NOLOWMEM
Requires that the /PAE switch be present and that the system have more than 4 GB of physical memory. If these conditions are met, the PAE-enabled version of the Windows kernel, Ntkrnlpa.exe, won't use the first 4 GB of physical memory. Instead, it will load all applications and device drivers, and allocate all memory pools, from above that boundary. This switch is useful only to test device driver compatibility with large memory systems.

/NOPAE
Forces Ntldr to load the non-Physical Address Extension (PAE) version of the Windows kernel, even if the system is detected as supporting x86 PAEs and has more than 4 GB of physical memory.

/NOSERIALMICE=[COMx | COMx,y,z...]
Obsolete Windows NT 4 qualifier-replaced by the absence of the /FASTDETECT switch. Disables serial mouse detection of the specified COM ports. This switch was used if you had a device other than a mouse attached to a serial port during the startup sequence. Using /NOSERIALMICE without specifying a COM port disables serial mouse detection on all COM ports. See Microsoft Knowledge Base article Q131976 for more information.

/NUMPROC=
Specifies the number of CPUs that can be used on a multiprocessor system. Example: /NUMPROC=2 on a four-way system will prevent Windows from using two of the four processors.

/ONECPU
Causes Windows to use only one CPU on a multiprocessor system.

/PAE
Causes Ntldr to load Ntkrnlpa.exe, which is the version of the x86 kernel that is able to take advantage of x86 PAEs. The PAE version of the kernel presents 64-bit physical addresses to device drivers, so this switch is helpful for testing device driver support for large memory systems.

/PCILOCK
Stops Windows from dynamically assigning IO/IRQ resources to PCI devices and leaves the devices configured by the BIOS. See Microsoft Knowledge Base article Q148501 for more information.

/RDPATH=
Specifies the path to a System Disk Image (SDI) file, which can be on the network, that the system will use to boot from. Often used in conjunction with the /RDIMAGEOFFSET= flag to indicate to NTLDR where in the file the system image starts.

/REDIRECT
Introduced with Windows XP. Used to cause Windows to enable Emergency Management Services (EMS) that reports boot information and accepts system management commands through a serial port. Specify serial port and baudrate used in conjunction with EMS with redirect= and redirectbaudrate= lines in the [boot loader] section of the Boot.ini file.

/SAFEBOOT:
Specifies options for a safe boot. You should never have to specify this option manually, since Ntldr specifies it for you when you use the F8 menu to perform a safe boot. (A safe boot is a boot in which Windows only loads drivers and services that are specified by name or group under the Minimal or Network registry keys under HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot.) Following the colon in the option you must specify one of three additional switches: MINIMAL, NETWORK, or DSREPAIR. The MINIMAL and NETWORK flags correspond to safe boot with no network and safe boot with network support, respectively. The DSREPAIR (Directory Services Repair) switch causes Windows to boot into a mode in which it restores the Active Directory directory service from a backup medium you present. An additional option you can append is (ALTERNATESHELL), which tells Windows to use the program specified by the HKLM\SYSTEM\CurrentControlSet\ SafeBoot\AlternateShell value as the graphical shell rather than to use the default, which is Windows Explorer.

/SDIBOOT=
Used in Windows XP Embedded systems to have Windows boot from a RAM disk image stored in the specified System Disk Image (SDI) file.

/SOS
Causes Windows to list the device drivers marked to load at boot time and then to display the system version number (including the build number), amount of physical memory, and number of processors.

/TIMERES=
Sets the resolution of the system timer on the standard x86 multiprocessor HAL (Halmps.dll). The argument is a number interpreted in hundreds of nanoseconds, but the rate is set to the closest resolution the HAL supports that isn't larger than the one requested. The HAL supports the following resolutions: Hundreds of nanoseconds Milliseconds (ms) 9766 0.98 19532 2.00 39063 3.90 78125 7.80 The default resolution is 7.8 ms. The system timer resolution affects the resolution of waitable timers. Example: /TIMERES=21000 would set the timer to a resolution of 2.0 ms.

/USERVA=
This switch is only supported on Windows XP and Windows Server 2003. Like the /3GB switch, this switch gives applications a larger address space. Specify the amount in MB between 2048 and 3072. This switch has the same application requirements as the /3GB switch and requires that the /3GB switch be present. Applies to 32-bit systems only.

/WIN95
Directs Ntldr to boot the Consumer Windows boot sector stored in Bootsect.w40. This switch is pertinent only on a triple-boot system that has MS-DOS, Consumer Windows, and Windows installed. See Microsoft Knowledge Base article Q157992 for more information.

/WIN95DOS
Directs Ntldr to boot the MS-DOS boot sector stored in Bootsect.dos. This switch is pertinent only on a triple-boot system that has MS-DOS, Consumer Windows, and Windows installed. See Microsoft Knowledge Base article Q157992 for more information.

/YEAR=
Instructs the Windows core time function to ignore the year that the computer's real-time clock reports and instead use the one indicated. Thus, the year used in the switch affects every piece of software on the system, including the Windows kernel. Example: /YEAR=2001. (This switch was created to assist in Y2K testing.)
Thanks to Jonas Fischer for pointing out the PCILOCK and NOSERIALMICE switches. Thanks to Rob Green for information on the FASTDETECT switch.