I had a perfectly working computer until yesterday when I went to Microsoft and allowed it to do and "Automatic Update". After that, the computer has been on a continuous loop of starting up, showing the Windows splash screen, then the "blue screen of death, then the black screen with startup options.

The blue screen of death has this error message...."Stop c0000218 {Registry File Failure} The registry cannot load the hive (file): or its log or alternate. It is corrupt, absent, or not writeable."

The computer has Windows XP on it. I have run a BIOS quick test on the hard drive, which failed once with an error code of "D202W0" then passed the same test. I have rund a BIOS comprehensive test, which failed, and gave the error code "B101WO".
I cannot start the computer in ANY mode. I want my computer back.

Any help?