Microsoft small business knowledge base

Article ID: 99743 - Last Review: February 27, 2007 - Revision: 2.2

This article was previously published under Q99743
For a Microsoft Windows XP version of this article, see 314081  ( ) .


Windows (specifically Ntldr) uses the Boot.ini file 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. To change the contents of this file easily, use the System tool in Control Panel.


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 list describes the data in the preceding Boot.ini file:
  • "Timeout" specifies the amount of time Windows waits before choosing the default operating system
  • "Default" specifies the default operating system.NOTE: When 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:

    • NT

  • "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 named "scsi(1)".

    NOTE: If the system uses IDE, EIDE, ESDI drives, or a SCSI adapter with no built in BIOS replace "SCSI" with "Multi".
  • "disk(0)" refers to physical disk 1.
  • 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 for each 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).
  • Multi-boot will look at the \Winnt folder 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.
  • The /SOS switch can be added to display driver names while they are being loaded during the Windows boot. By default, the OS Loader screen only echos progress dots.
  • The "Previous Operating System on C:\" parameter implies that it is MS-DOS, because "C:\" is an MS-DOS path.

  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows NT Advanced Server 3.1
  • Microsoft Windows NT Server 3.5
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
  • Microsoft Windows NT Workstation 3.1
  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
kbinfo kbother KB99743
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