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How to edit / modify computer boot.ini file

Warning: Incorrectly editting boot.ini file will cause your computer fail to boot up!

The contents of the Boot.ini file determine what options will appear in the startup menu for Windows XP, 2K, NT. Boot.ini is a small file in the root of the system partition which is nearly always the C: drive. The computer uses the system partition during early bootup before loading the OS from the OS's boot partition which may, or may not, also be the system partition.

Boot.ini is not normally visible in Windows Explorer as it has the Read-only, System, and Hidden attributes set.

The method you use to edit will depend on your circumstances. The safest method is to use Startup and Recovery which eliminates mistakes or typing errors but it has limited functionality. The most thorough method is a manual edit from Windows or MS-DOS.

Be careful with your typing when you edit Boot.ini. And remember that spaces are as important as content. The following are the samples:

This is a sample of a default Boot.ini file from a Windows XP Professional computer.
[boot loader]
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect

This is a sample of the above Boot.ini file with a previous installation of Windows 2000 on a separate partition.
[boot loader]
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP Professional" /fastdetect
multi(0)disk(0)rdisk(0)partition(2)\WINNT="Windows 2000 Professional" /fastdetect

The multi() syntax indicates to Windows that it should rely on the computer's BIOS to load system files. It's virtually always set to 0 (zero). If the SCSI() notation is used instead of multi() it indicates that Windows will load a boot device driver (NTBOOTDD.SYS) and use that driver to access the boot partition.

For disk() syntax, it is always 0 when multi(0) is used because the INT 13 call is involked. If scsi() is used then the number will be the SCSI ID of the target disk. For the vast majority of users the correct syntax will be multi(0)disk(0).

rdisk() refers to physical hard disks and starts counting from 0. Therefore rdisk(1) refers to a second disk. Every hard disk counts, not just disks with OSs installed. The Primary Master hard disk is always rdisk(0). If a Primary Slave exists, it has priority over any Secondary disk(s). If a Secondary Master exists, it has priority over a Secondary Slave. Use the following table for your reference:

             PrimaryMaster   PrimarySlave   SecondaryMaster   SecondarySlave
1 disk  ->      rdisk(0)
2 disks ->      rdisk(0)        rdisk(1)
2 disks ->      rdisk(0)                       rdisk(1)
2 disks ->      rdisk(0)                                         rdisk(1)
3 disks ->      rdisk(0)        rdisk(1)       rdisk(2)
3 disks ->      rdisk(0)        rdisk(1)                         rdisk(2)
3 disks ->      rdisk(0)                       rdisk(1)          rdisk(2)
4 disks ->      rdisk(0)        rdisk(1)       rdisk(2)          rdisk(3)
For partition() syntax, a number is allocated to each partition in the order that they occur on the hard disk specified by rdisk(). It starts counting from 1, and Primary partitions on that disk are counted first. Therefore partition(2) is the second Primary partition on the disk. Here is an example:

rdisk(0)partition(1) refers to the first hard disk and its first partition. An example of the third partition on a second hard disk would be rdisk(1)partition(3).

Finally, use "bootcfg /rebuild" to rebuild the boot.ini file.

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