OK, last week my computer failed to boot, the HD LED came on, the Power LED didn't and all the fans started spinning. Holding the power button turned it off.
I checked for loose connections but found nothing so I reset the CMOS.
This time it booted with the message CMOS checksum error, loaded from defaults (or similar), I hit F1 as instructed and it continued to load windows.
All was well for a time, with the computer quite happy to boot as normal but today the same thing happened.

Specs are as follows:
Mobo: ASUS M2N32-SLI Deluxe
CPU: AMD Athlon 64 X2 5600+ (not overclocked)
RAM: 2*2GB OCZ 667MHz DDR2
GPU: 8800GT 512MB
PSU: 600W FSP Group
Running Vista Home Premium, though that should make no difference.

This was a custom build by a company called PCSpecialist 2 years ago but the RAM, CPU and GPU I have put in since as upgrades.
Does anyone know what might cause this? I don't want to have to reset my CMOS on a weekly basis and I am worried that it is a symptom of something worse to come.

I have probably missed something in this question let me know if there is information you need.

Cheers

I did think that, but surely that would only make it revert to the default settings rather than make it not get to the POST?
Can't hurt to order a new battery though I suppose.

OK, it has got worse, last night I had to reset the CMOS again and this morning moving the jumper wouldn't do it first time, I had to take the battery out (which involves removing my graphics card so isn't exactly something I can do every day. I have swapped out the battery for a new one and the same thing happened so it is not that.

I'm really not sure about updating the BIOS though as I suspect the CMOS chip is damaged in which case I am worried that the flash might fail leaving me with nothing. I don't have the original version that was on the board when I got it (because that had poor RAM stability, so I got blue screens all the time) and since the version I have most of the updates are for new CPUs rather than fixes.

So, can anyone confirm that a faulty CMOS chip could cause this behaviour? and should I be worried about updating the BIOS should this be the case?

PS: I'm going to be leaving my computer in sleep mode rather than turning it off until I can fix this or I get a new one.

My spare PSU is not up to the task unfortunately, it is 350W. I have already started dumping stuff on my second drive. As for minimum configuration, now I have removed my TV card (which I managed to forget in the original post) the only thing I can take out is the second Hard disk and the second RAM stick.

Trouble is, I am not sure I really want to turn it off at the moment, it took me ages to get it to boot this morning.

I'm loading Everest Ultimate Edition now to check voltages and will report back. I'm not sure I will be able to stress the system to failure with it though, it didn't crash with half an hour of UT3 last night, once it boots it seems to be fine.

John, those numbers all look fine to me and UT3 is certainly a good stress test. If it is the PSU, and we don't know either way, it may only be glitching on a cold start. Your diagnostic procedure is good. Let me know if you want to bounce any ideas off me or have me look at other results.

Thank you for all your help.
Whilst I know it could be the PSU, I have decided that as it is likely to be the motherboard that is faulty I am just going to take the plunge and upgrade[1] to a Core i7 system. I have been wanting to do this for a while anyway, I was just lacking the justification.
Thank you again. I may start another thread soon for suggestions on components...

Cheers.

[1] Is it still called an upgrade when you are going to replace nearly every component?

Ah yes, exactly what I was referring to. :)