Even if you reinstall, you still haven't isolated the cause of the problem.

The 0x7B stop code and the corrupt registry file (\system32\config\system) point to a failing device in your storage subsystem.  Check your hard disk and IDE cables.

Your hard drive maker probably offers a drive test utility as a free download.  Get a copy and run it.  Make sure there are no bad blocks on the drive.

Also, double check your IDE cables.  Make sure they are all 80-conductor.  Also check cable lengths.  Any IDE cable longer than 18" is bad and should be thrown out immediately.  Likewise for those sliced/narrow IDE cables.

It may also be your IDE controller, especially if you are using a cheapo IDE RAID controller.

Another oustide possibility is that it's bad memory.  It may be worth running an overnight cycle of Memtest86.