BSOD occours at random several times daily.

That looks great macca747, and no errors in Prime95?

Also, did you see this post?

OK Update. I ran the memtest86 for over 15 hours, 9 passes, no errors.

I ran the sfc /scannow, some errors were found & repaired, log attached.

So by my reckoning, I've discounted; the RAM, the sound card, the display card (nvida) although with the display there is an annoying black screen x2 every now & again.

2012-05-12 12:23:12, Info CSI 0000012b [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:24:12, Info CSI 00000155 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:24:12, Info CSI 00000157 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:24:13, Info CSI 00000159 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slmgr.vbs" from store
012-05-12 12:24:33, Info CSI 00000168 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:26{13}]"systemcpl.dll" from store
2012-05-12 12:24:54, Info CSI 0000017b [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"user32.dll" from store
2012-05-12 12:25:12, Info CSI 0000018c [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"winlogon.exe" from store
2012-05-12 12:25:19, Info CSI 00000192 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"winver.exe" from store
2012-05-12 12:28:00, Info CSI 0000020a [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:28:11, Info CSI 00000217 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"user32.dll" from store
2012-05-12 12:30:17, Info CSI 000002c8 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:30:34, Info CSI 000002dc [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:30:34, Info CSI 000002de [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slmgr.vbs" from store
2012-05-12 12:30:38, Info CSI 000002e4 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:26{13}]"systemcpl.dll" from store
2012-05-12 12:30:57, Info CSI 000002f7 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"winver.exe" from store
2012-05-12 12:31:21, Info CSI 00000316 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"user32.dll" from store
2012-05-12 12:31:21, Info CSI 00000318 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:31:21, Info CSI 0000031a [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slmgr.vbs" from store
2012-05-12 12:31:22, Info CSI 0000031c [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:26{13}]"systemcpl.dll" from store
2012-05-12 12:31:22, Info CSI 0000031e [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:31:22, Info CSI 00000320 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slmgr.vbs" from store
2012-05-12 12:31:22, Info CSI 00000322 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"winver.exe" from store
2012-05-12 12:31:22, Info CSI 00000324 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"user32.dll" from store
2012-05-12 12:31:22, Info CSI 00000326 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:31:23, Info CSI 00000328 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"winver.exe" from store
2012-05-12 12:31:23, Info CSI 0000032a [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:31:23, Info CSI 0000032c [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:31:23, Info CSI 0000032e [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"winlogon.exe" from store
2012-05-12 12:31:23, Info CSI 00000330 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:31:23, Info CSI 00000332 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:26{13}]"systemcpl.dll" from store
2012-05-12 12:31:23, Info CSI 00000334 [SR] Repair complete
2012-05-12 12:31:23, Info CSI 00000335 [SR] Committing transaction
2012-05-12 12:31:23, Info CSI 00000336 [SR] Cannot commit interactively, there are boot critical components being repaired
2012-05-12 12:31:23, Info CSI 00000337 [SR] Repairing 15 (0x000000000000000f) components
2012-05-12 12:31:23, Info CSI 00000338 [SR] Beginning Verify and Repair transaction
2012-05-12 12:31:24, Info CSI 0000033a [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"user32.dll" from store
2012-05-12 12:31:24, Info CSI 0000033c [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:31:24, Info CSI 0000033e [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slmgr.vbs" from store
2012-05-12 12:31:24, Info CSI 00000340 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:26{13}]"systemcpl.dll" from store
2012-05-12 12:31:25, Info CSI 00000342 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"ntoskrnl.exe" from store
2012-05-12 12:31:25, Info CSI 00000344 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slmgr.vbs" from store
2012-05-12 12:31:25, Info CSI 00000346 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"winver.exe" from store
2012-05-12 12:31:25, Info CSI 00000348 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"user32.dll" from store
2012-05-12 12:31:25, Info CSI 0000034a [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:31:25, Info CSI 0000034c [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"winver.exe" from store
2012-05-12 12:31:25, Info CSI 0000034e [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:20{10}]"sppwmi.dll" from store
2012-05-12 12:31:26, Info CSI 00000350 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:31:26, Info CSI 00000352 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:24{12}]"winlogon.exe" from store
2012-05-12 12:31:26, Info CSI 00000354 [SR] Repairing corrupted file [ml:48{24},l:46{23}]"\??\C:\Windows\SysWOW64"\[l:18{9}]"slwga.dll" from store
2012-05-12 12:31:26, Info CSI 00000356 [SR] Repairing corrupted file [ml:520{260},l:46{23}]"\??\C:\Windows\System32"\[l:26{13}]"systemcpl.dll" from store

That's more than a few. You should try running it again, although it may not do any good.

2012-05-12 12:31:23, Info CSI 00000336 [SR] Cannot commit interactively, there are boot critical components being repaired

So, you may need to do a clean install. Back in this post, you mentioned some bugs in the PC. I am going to say that you probably did not wipe the drive before you put your new OS on and these bugs were there and ate away at your OS. I would suggest wiping the HDD and reinstalling the OS. Hopefully your installation media is in good shape.

macca747 said:

Further Update.

Re-formatting the drive & re-installing didn't work - I got BSOD on 1st boot up after re-install !

Eventually traced problem, although in the tech specs for my system it says x64 is ok win7 x64 was not compatible with my system. I re-formatted again & am now running win7 x86 with no problems.

Thanks to all who tried to help me.

Yeah, I never even thought that might be the issue, given that your system is compatible with x64. It may be very likely that you have a bad processor. x86 does not use the full width of the data bus on an x64 processor. This may be why the errors don't occur when you are running an x86 OS. At any rate, I am happy that you have found a resolution.

Congratulations.