Well its not missing and its probably not corrupt. You get this message if something is writing too much data to the System subkey in the registry. Think about what you have installed lately.
Intel and ARC (RISC) systems have a design limit such that 16 megabyte (MB) of memory is available at this stage of the boot process and the following must fit in that available 16M RAM :
- boot drivers
- system registry hive
If the System registry hive exceeds 13MB, you get that error. To resolve the problem, you have to replace it with a backup version. Use the Repair Console tool to replace the backup copy of the System hive from the repair folder. If you do not have the Repair Console tool installed, you can run it from the Emergency Repair process:
- Start the computer by using the Windows CD-ROM or the Startup disk.
- When you see the “Welcome to Setup” message, press R for “repair.”
- Press C to run the Recovery Console tool.
- Select the installation that you want to repair.
- Type the administrator password. If this is a domain controller, you need to supply the password for Directory Services Restore Mode.
- Log on to the Recovery Console tool and type the following commands:
- cd system32\config
- ren system system.old
- ren system.alt systemalt.old
- cd system32\config
- Copy the backup of the System hive from either the %SystemRoot%\Repair folder or the %SystemRoot%\Repair\Regback folder if you run the Emergency Repair Disk Wizard from Windows Backup and Recovery tools.
You will need to restore the most recent copy of the System hive. Any programs that run as a service or hardware device drivers that you installed since you last ran the Emergency Repair Disk need to be re-installed.
To copy the default System hive, type the following command:
copy c:\winnt\repair\system to copy the default system hive
To copy the System hive that was backed up the last time that you ran the Emergency Repair Disk Wizard, type the following command:
After you run these commands, type exit at the command prompt to restart your computer.