Microsoft KB Archive/254274

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Purpose of the BOOT.INI File


The information in this article applies to:

  • Microsoft Windows NT Advanced Server
  • Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
  • Microsoft Windows NT Server versions 3.51, 4.0
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server


Thie article describes the Boot.ini file used by Windows NT during the starup process.


The Boot.ini file is used by Windows NT (specifically, Ntldr) to determine the operating system options to display during the startup (boot) process. Boot.ini is flagged as a read-only, system file by default and should not require any manual modification. You can change its contents easily from Control Panel by choosing the System icon.

The following is a typical Boot.ini file:

[boot loader] timeout=30 default=scsi(0)disk(0)rdisk(0)partition(1)\winnt

[operating systems] scsi(0)disk(0)rdisk(0)partition(1)\winnt = "Windows NT" /NODEBUG C:\ = "Previous Operating System on C:\"

The following are line-by-line explanations of the above Boot.ini file:

[boot loader] timeout = 30

Timeout specifies the amount of time Windows NT waits before choosing the default operating system.


Default specifies the default operating system. Note: Whenever the operating system is Windows NT, the new storage path syntax is used. For more information on this syntax, query on the following words in the Microsoft Knowledge Base:


[operating systems] scsi(0)disk(0)rdisk(0)partition(1)\winnt = "Windows NT" /NODEBUG C:\ = "Previous Operating System on C:\"

scsi(0) means that the primary controller (usually the only one) is responsible for the device. If there were two SCSI cards and the disk was hanging off the second one, it would be called scsi(1).

disk(0) refers to physical disk 1.

rdisk(0) - The rdisk() parameter refers to which SCSI logical unit (LUN) to use, which could be a separate disk, but the vast majority of SCSI setups have only one LUN per SCSI ID.

partition(1) in this example is the only partition on the first drive in the computer. If there were two partitions, C and D, C would be partition(1) and D would be partition(2).

\winnt is the directory that multi-boot will look at to boot from one of the specified SCSI card's disk and partition.

/NODEBUG specifies that there's no debugging information being monitored. Debugging information is only useful for developers and does slow down Windows NT somewhat.

The /SOS switch can be added to display driver names while they are being loaded during the Windows NT boot. By default, the OS Loader screen only echos progress dots.

The Previous Operating System on C:\ implies that it is MS-DOS, because "C:\" is an MS-DOS path.

Additional query words: prodnt

Keywords : kbother KBW2KHOME
Issue type : kbinfo
Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351xsearch kbWinNT350xsearch kbWinNT400xsearch kbWinNTW350 kbWinNTW350xsearch kbWinNTW351xsearch kbWinNTW351 kbwin2000AdvServ kbwin2000AdvServSearch kbwin2000Serv kbWinNTSsearch kbWinNTS400xsearch kbWinNTS400 kbWinNTS351 kbWinNTAdvSerSearch kbwin2000ServSearch kbwin2000Search kbwin2000ProSearch kbwin2000Pro kbWinNTS351xsearch kbWinAdvServSearch

Last Reviewed: November 23, 2000
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