If you receive the following message when you attempt to start Windows NT:
Windows NT could not start because the following file is missing or corrupt:
\%winnt%\SYSTEM32\CONFIG\SYSTEMHardware Profile/Last Known Good menu
the System subkey of the HKEY_LOCAL_MACHINE registry hive is too large.
Microsoft says that the only resolution is to use an Emergency Repair Disk or perform a reinstallation of Windows NT.
There is another option you can try first:
1. Boot to an alternate install of Windows NT.
2. Use the technique in tip 182 to remove entries from each of the control sets that are no longer needed.
Likely candidates are the Services subkey and matching entries in the Enum\Root subkey.