My computer, which I have had for about 4 years, running Win 2000, started crashing recently. It works fine for about 45 minutes, then freezes, and after a few seconds the screen goes black with only a frozen cursor arrow. When I switch it off, the NumLock light on the keyboard stays on. This goes off when I switch it off at the PSU.

If I try to reboot it straight away, it doesn't boot properly. If I leave it for a while and switch it off at the PSU, it boots normally and runs for a short while before freezing again.

I think this is a hardware problem, possibly overheating somewhere. Does anyone have a clue of what I should do to fix it? I have run virus checks, which have found nothing. I don't think it is an OS problem as it runs okay from cold. Strangely, it does not beep anymore when booting up.

Any ideas would be appreciated.

If the numlock stays on, it usually means that the PC has gone into Standby mode and there's a power setting in control panel to regulate this.

I don't know why it goes into standby but that's what I reckon it's doing.

yup, suspishio maybe right double check your settings maybe you just set the system to either hibernate or standby mode, if you suspect that it is a hardware problem then double check your cpu fan and check also if there's enough thermal compound on your heatsink...if still the same try using another PSU..