Your computer does not start if the SYSTEM hive is too large

When you start your computer, you may receive the following error message:

In Windows NT 4.0 In Windows 2000:

This issue may occur if Windows cannot allocate enough memory to the SYSTEM hive. The SYSTEM hive is typically around 3 MB, but when it is highly fragmented or damaged, its size may increase greatly. If a large number of programs have been installed and removed on your computer, or if the computer shares a large number of resources, the registry may become too large.

To resolve this issue, use the following methods in the order in which they are presented.

Method 1: Replace the SYSTEM Hive

Important: The WINNT\Repair folder contains a copy of the SYSTEM hive in the SYSTEM file. The SYSTEM hive is updated if you run the Rdisk.exe utility (available only with Windows NT), and then select the Update repair information option. If you have recently updated the SYSTEM hive by using the Rdisk.exe utility, go directly to "Method 3".

Replace the SYSTEM hive in the Config folder with the SYSTEM hive from the Repair folder. To do so, follow these steps:

1. Start the computer by using the Windows Setup floppy disks or the Windows 2000 CD-ROM. At the "Welcome to Setup" screen, press R to repair, and then press C to start the Recovery Console.
2. Type the number for the appropriate Windows installation, and then type the Administrator account password.
3. To copy the SYSTEM file from the WINNT\Repair folder to the WINNT\System32\Config folder, type the following command, and then press ENTER:
   copy c:\winnt\repair\system c:\winnt\system32\config\SYSTEM
   . If you receive a prompt to overwrite the file, press Y, and then press ENTER.
4. Restart the computer.

Note: If you use the file allocation table (FAT) file system, use a Microsoft Windows 98 startup disk to start the computer.

Method 2: Restore the SYSTEM File from the SYSTEM.ALT Backup File

Use this method if the WINNT\Repair\System file is old and the Rdisk utility has not been run to update the repair information.

1. Start the computer by using the Windows Setup floppy disks or the Windows 2000 CD-ROM. At the "Welcome to Setup" screen, press R to repair, and then press C to start the Recovery Console.
2. Type the number for the appropriate Windows installation, and then type the Administrator account password.
3. Type the following command, and then press ENTER:
   copy c:\winnt\system32\config\system.alt c:\winnt\system32\config\SYSTEM
   . When you are prompted to overwrite the file, press Y, and then press ENTER.
4. Restart the computer.

Method 3: Restore the SYSTEM Hive from Backup

If the preceding methods do not resolve the issue, create a parallel installation of Windows, and then restore the SYSTEM hive from a tape backup to the original WINNT\System32\Config folder.

When Windows starts, its memory is limited to 16 MB. If the SYSTEM hive exceeds the available memory, the computer cannot start and you receive one of the error messages that listed in the "Symptoms" section of this article.