Windows XP-sp2 restarts during boot sequence

Hello all,

I have found your forum very useful on the past few days. You are doing a great job thanks a lot.

My problem started a few days ago, every time I power on my PC it restarts before it boots all the way. It shows the screen with the bios version on it and begins booting XP. The bar on the bottom does move, so i know it is not frozen. About 15 seconds after starting the computer the computer restarts.

when i press F8 and seleted "disabled automatic restart on system failure"
it showed me BSOD with the following error message:
PAGE_FAULT_IN_NONPAGED_AREA and the dump code is:
0x00000050

I have tried the following without luck:

1. last good configuration - same behavior.
2. safe mode (all possible configurations) still restarts when gets to mup.sys
3. win xp install disk - pressed R -recovery console as i get to windows selections it gets BSOD with the same error
4. connected the HD to other computer (working) with similar HW - same BSOD - cleans HW connections
4. i followed your instructions written in "read and me first " of your forum, under "Windows XP Malware Removal/Cleaning Procedure" i jumped directly to "Alternative Scans"
a. i used Avira Rescue CD and scanned the computer but it didn't help.
b. I built UBCD4Win which looked promising but when it loads up and i try to start some program (for instance regedit(remote) or scanning for malwares) it also gets BSOD with the same error

I don't know what to do any more...
Any help would be GREATLY appreciated.
Thanks
Refael.