Article ID: 314081 - Last Review: August 1, 2005 - Revision: 1.5

The purpose of the Boot.ini file in Windows XP

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This article was previously published under Q314081
For a Microsoft Windows 2000 version of this article, see 99743  (http://support.microsoft.com/kb/99743/ ) .
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INTRODUCTION

This article describes the purpose and contents of the Boot.ini file.

MORE INFORMATION

Windows (specifically Ntldr) uses the Boot.ini file to determine which operating system options to display when the Startup program is running. By default, Boot.ini is not flagged as a read-only system file and generally does not require any manual modification.

If you must change the contents of this file, use the System tool in Control Panel:
  1. Click Start button, click Control Panel, and then double-click System.
  2. Click the Advanced tab, and then click Settings under Startup and Recovery.
Typically, the Boot.ini file contains the following data:
[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 meaning of the data in the Boot.ini file:
  • The "timeout" variable specifies how long Windows waits before choosing the default operating system.
  • The "default" variable specifies the default operating system.
  • The term "scsi(0)" means that the primary controller (that is frequently the only controller) is responsible for the device. If there are two SCSI controllers, and the disk is associated with the second controller, the controller is named "scsi(1)".

    If the system uses IDE, enhanced IDE (EIDE), or Enhanced Small Device Interface (ESDI) drives, or if the system uses a SCSI adapter that does not have a built-in BIOS, replace "scsi" with "multi".
  • The term "disk(0)" refers to the SCSI logical unit (LUN) to use. This may be a separate disk, but most SCSI setups have only one LUN for each SCSI ID.
  • The term "rdisk(0)" refers to physical disk 1.
  • The term "partition(1)" is the partition on the first drive in the computer. If there are two partitions, partition C is partition(1) and partition D is partition(2).
  • A multi-boot parameter calls for checking the Winnt folder to start from a specified SCSI controller's disk and partition.
  • "/NODEBUG" specifies that no debugging information is being monitored. Debugging information is useful only for developers.
  • You can add the /SOS option to display driver names while the drivers are being loaded. By default, the OS Loader screen only shows progress dots.
  • "Previous Operating System on C:\" implies that the "previous operating system" is MS-DOS, because "C:\" is an MS-DOS path.
APPLIES TO
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
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Keywords: 
kbenv kbinfo kbsetup KB314081