You receive a "Windows could not start because the following file is missing or corrupt: Isapnp.sys" error message at startup

When you try to start Microsoft Windows XP or Microsoft Windows 2000 , you may receive one of the following error messages, depending on your operating system.

Windows XPWindows 2000

This issue may occur if the Isapnp.sys file is damaged or is not present in the path that the error message specifies.

To resolve this issue, use Recovery Console to replace the Isapnp.sys file.

Windows XP

To replace the Isapnp.sys file in Windows XP, follow these steps:

1. Start the computer from the Windows XP CD-ROM.
2. At the Welcome to Setup screen, press R to start Recovery Console.
3. If you have a dual-boot or a multiple-boot computer, type the number that corresponds to your Windows XP installation when you are prompted to select the Windows installation to log on to, and then press ENTER.
4. When you are prompted for the Administrator password, type the password, and then press ENTER.
   
   Note If the administrator password is blank, just press ENTER.
5. At the C:\Windows prompt, type the following command, and then press ENTER:
   ren c:\windows\system32\drivers\isapnp.sys isapnp.old
   Note The steps in this article assume that you installed Windows XP to the C: drive. The actual location of your Windows installation may vary.
6. At the C:\Windows prompt, type the following command, and then press ENTER:
   expand cd-romdrive:\i386\isapnp.sy_ c:\windows\system32\drivers\isapnp.sys
   For example, type:
   expand d:\i386\isapnp.sy_ c:\windows\system32\drivers
7. After the file is successfully expanded, type exit, and then press ENTER to exit Recovery Console.
8. Restart the computer.

Windows 2000

To replace the Isapnp.sys file in Windows 2000, follow these steps:

1. Start the computer from the Windows 2000 CD-ROM.
2. At the Welcome to Setup screen, press R to repair, and then press C to start Recovery Console.
3. At the C:\Winnt prompt, type the following command, and then press ENTER:
   expand cd-romdriveletter:\i386\isapnp.sy_ c:\winnt\system32\drivers\isapnp.sys
   For example, type:
   expand d:\i386\isapnp.sy_ c:\winnt\system32\drivers
   Note The steps in this article assume that you installed Windows 2000 to the C: drive. The actual location of your Windows installation may vary.
4. After the file is successfully expanded, type exit to exit Recovery Console.
5. Restart the computer.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: