System will not post unless it has warmed up

[chrestomanci]

Hi, I am asking about my Dad's PC which I built for him a number of years back.

In short, it will only post and boot normally if it has been running a while. If he turns if off overnight or longer, then when he first turns it on it does not post, instead the screen fills with random characters. He has to leave it in this crashed state for an hour or more before power cycling it, when it boots normally.

Does anyone recognise the symptoms?

The PC has a quality Enermax PSU. (It was mine though it is 9 years old). The CPU and Mobo is AMD S939, so you can probably guess that it is a few years old.

Other symptoms:

If you run Memtest86 (once the system is warm) then the tests all pass.

Every time my dad attempts to start Nero to use the DVD writer, the system bluescreens.

My Dad suspects that the USB devices he has connected may be making the system less stable, but I am not convinced. He has a Microsoft wireless keyboard and mouse, an inkjet printer and a scanner. Nothing unusual.

Any ideas?

[Queelis]

I had a cold boot problem with my PC (though it would sometimes not even restart after it's been running for a while), turned out to be a faulty motherboard.

Well, for starters disconnect everything that's not needed to boot (the DVD burner, for example), then try.

Then I'd suspect the PSU (yes, good, but 9 years old). Take the PSU from your own PC and test it - the easiest way, since all are compatible.

If the problem persists, I'd say it's the mobo. You can check for blown capacitors, of course. It there are any - you need a new mobo (you'll have to look for a second hand one, though - I doubt you'll find any new ones).

By the way - what happens when you try to read some CD/DVD?

[chris_argyle]

I had a cold boot problem that was caused because the ram was auto setting it's voltage to a standard rather than the higher recommended level. Might be worth checking.