Comp still screwed, hardare problem

Reinstalled XP, replaced the PSU and evey so often the bloody thing completely freezes or doesnt manage to complete the POST test thing that gives a "beep" if everything is ok, even if it does give this beep sometimes it still just freezes when windows is fully loaded and has been running for like 10 minutes.

I can\'t exactly buy another motherboard and test it out to see if thats the problem so is there any other way of narrowing down whats causing this? like a motherboard testing program or something?

If it\'s not the PSU or mobo, I think it would be bad ram.

http://oca.microsoft.com/en/windiag.asp
http://www.memtest86.com

did you reset the CMOS?  There should either be a jumper you have to switch or a button on your Mobo.

would this be reset automatically if i reinstalled windows? if not ill look for it.

I tried changing out the CPU but the same thing still happens ocaisionally, also the sound ocasianlly swaps from 2 speakers to just one and there are loads of pops and squeaks coming thru the speakers when i play music and somtimes just randomly when theres no music playing, ive got an integrated sound card on the mobo, u think the mobo is at fault?

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remove the onboard bios battery, remove power from psu.. leave for a few minds, then wack the battery back in and start. It will have reset the bios.
Take notice of the beeps its doing, their length, amount of beeps etc. Then google Bios Beep warnings in google. It will tell you what they relate too.