Hi everyone, I really need help on this one guys:

I have an ASUS CUBX-E mainboard in my PC. I have been using this setup for the past 6+ yrs with no issues ever. Earlier had Win Me and currently using XP Pro.
But for the past three weeks I am facing a strange problem : The registry of windows xp is getting corrupted quite frequently. I have re-formatted and re-installed windows xp pro several times but its registry is getting corrupted frequently, sometimes immediately after XP installation is finished and I reboot and I get the following error :

1. "Windows could not start because the file c:\windows\system32\config\system is corrupt or missing."
2. "Error : \system root\system32\hal.dll missing"

I have tried repairing the windows installation and the registry using recovery console from the windows xp cd but the errors reappears. Sometimes I get the error within few minutes after windows installation completes. However, I would like to emphasize here that windows xp installs everytime without error. Also Windows XP Pro with SP2 has all the drivers for my PC, so I never have to install any other drivers. So that rules out a driver clash or mismatch.

1. The problem begins after the installation.
2. Error 1 is much more common and as per microsoft is related to corrupt registry.
3. I have also tried using different xp cd but it does not help.
4. I have low-level formatted the hdd but it did not help.
5. I have changed the IDE cables but that also did not help.
6. the hdd has no bad sectors and I have tried using both NTFS and FAT32 install. No help.
7. The error/errors may appear after the first restart or after a few days. But they DO return.
8. I have RUN memory diagnostics by microsoft (Memdiag) ; DocMemory and Memtest86+ 1.7 BUT NO ERRORS --- EVER !!!!
9. TESTCPU program shows no errors in processor. Benchmarks using Sandra 2002 are comparable to Sandra test systems.
10. HDD diagnostic DFT v4.05 and v4.06 show NO ERROR in my Hitachi HDD (80 GB).
11. chkdsk /r sometimes helps (windows is able to start) but it reports NO BAD SECTORS either.
12. when the PC is running I am able to install my programs (MS-office 2003, Acrobat reader, winrar, etc.) and I get no errors installing or running them.
13. I have scanned the PC for viruses using Norton 2008 and Mcafee 2008 (Eval. versions) with latest definitions but they found no viruses.
14. I do get BSOD errors like : 8E,50,7F,0A,77 etc... but anyone who runs windows knows that they are a part of everyday computing. But RAM tests show no errors.

15. As a last resort I am using Windows Me. It also shows registry corruption but recovers on using "scanreg" tool.
However, if I do not run scanreg and try to boot into safe mode or normal, Me shows "new hardware found" but the hardware name is missing !!!!
I tried installing the usual drivers I have to install in Me but it rejects them all (No suitable driver found).
So which "new hardware" is Me finding and trying to install????
Bootlog.txt of Me shows these cryptic errors :
[0010FD1F] DEVICEINIT = CONFIGMG
[0010FD1F] ASD: failing Unnamed problem, d=HTREE\RESERVED\0, rc=00000005[0010FD1F]
[0010FD1F] ASD: failing Unnamed problem, d=HTREE\ROOT\0, rc=00000005[0010FD1F]
[0010FD1F] ASD: failing Unnamed problem, d=P00000010, rc=00000005[0010FD1F]
[0010FD1F] DEVICEINITSUCCESS = CONFIGMG

LoadStart = pnpdrvr.drv
LoadFail = pnpdrvr.drv Failure code is 0002

Init =
LoadStart = DISPLAY.drv
LoadFail = DISPLAY.drv Failure code is 0002

LoadStart = vga.drv
LoadSuccess = vga.drv
LoadStart = DISPLAY.drv
LoadSuccess = DISPLAY.drv
InitDone = DISPLAY
Init = Display Resources
InitDone = Display Resources

As you can see although pnpdriver and display drv fail yet they load up later (maybe after scanreg). I would also like to add that once Me OR XP are up and running they run stable. Problems come either on reboot (more in XP) or on cold starts (more in Me).

After scanreg Me boots up fine. I am able to use all my programs and browse the web. In fact I am posting this message from the same PC with Me up an running (IE6.0, DX9, Mcafee virusscan pro 2005)

My complete PC specs are :

1. ASUS CUBX-E motherboard with P-III 750 Mhz and 256 MB PC-133 SDRAM [Windows xp pro with sp2.]
2. Hitachi 80 GB hdd as master on promise ata-100 controller.
3. LG 52x CD-RW drive GCE-8527B as secondary slave on 440BX IDE
4. Sapphire ATI Radeon 7000 AGP with 64 MB DDR RAM (IRQ 11)
5. Compex RE100ATX lan card (IRQ 12)
6. Pctel 56k softmodem (IRQ 5)
7. Yamaha soundcard (IRQ 10)
8. Onboard Promise ATA-100 CONTROLLER (PDC-20265) (IRQ 10)
9. USB ports and hub (IRQ 5)
PCI Rev.2.2

I have been using this configuration with XP pro for the last three years without any problems. I am unable to locate any error in the PC RAM, hdd, add-in cards, processor, yet I am repeatedly getting this problem. the frequent crashes and BSOD indicate a RAM problem but then why do Memdiag ; DocMemory and Memtest86+ show no error ???? The problem is more severe in XP than Me. (XP uses more resources though)

Could it be a BIOS issue ? OR power supply ?

I am totally baffled !!! Really need help on this.
Any advise/suggestion would be useful.