Sometimes a Windows XP based PC will fail to boot with a bluescreen error about a certain registry hive being corrupted. It will read something like...

\SystemRoot\System32\Config\Software is corrupt or...

\SystemRoot\System32\Config\System is corrupt

\SystemRoot\System32\Config\Default is corrupt

Essentially all you have to do is boot up the recovery console (with your Windows XP CD) and then firstly run a disk check with : Chkdsk /p This will sometimes fix the problem which is the result of a disk corruption (normally bad sectors). If the drive is still within warantee return to manufacturer for a refund. If this fails then restore the specific hive (e.g. Software/ Default / System etc.) for the repair folder of the windows install (c:\windows\repair\). The hive needed to be restored will be indicated by the blue screen stop error. This is accomplished by simply using the copy command from within the recovery console.