The
Windows 2000 registry comprises a handful of hive files located in the
%systemroot%\System32\Config folder. When Windows 2000 starts, it builds the
registry from these files. One of the registry files is the SYSTEM hive, and a
corrupted or fragmented SYSTEM hive can prevent the system from booting.

When
the system first boots, it’s limited to 16 MB of memory. A highly fragmented
SYSTEM hive can cause the maximum amount of memory to be exceeded, thereby
preventing the system from booting. Defragmenting the
file can be a quick fix. You can defragment the
system drive inside of Windows 2000, which is a good reason to do it on a
regular basis; but if your system has sufficient contiguous free space, you can
overcome the problem through the Recovery Console (RC).

  1. Boot the system to the RC and
    then use the CD command to change to the
    %systemroot%\System32\Config folder.
  2. Rename the existing SYSTEM
    file to SYSTEM.OLD.
  3. Use the command COPY
    SYSTEM.OLD SYSTEM     to create a new, unfragmented
    copy of the SYSTEM hive.
  4. Exit the RC to restart the
    system.

If
creating an unfragmented copy of the SYSTEM hive
doesn’t fix the problem, it’s possible that the SYSTEM hive file is corrupted.
If you have a good version backed up in the %systemroot%\Repair or %systemroot%\Repair\Regback
folder, boot to the RC again and then copy the backup SYSTEM hive file
to the %systemroot%\System32\Config folder.

Note:
As always, we’ll remind you that editing the registry can be risky, so be sure
you have a verified backup before making any changes.

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