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.