OK, I will try to explain my PC'S issue as best I can, and hopefully someone will be able to suggest a fix, other than the obvious replace it answer :)

At the start of the week, I was happily surfing with FF3 before work, and turned off the desktop speakers and fittttt, I had a message on the monitor that said no signal, then a blank monitor.

The PC was still showing a disc activity light, although it wasn't doing anything(the light that is).

So wiggle mouse, tap keyboard, click mouse, nothing, it's a dead stick, strange me thinks.

So I hit the power button, and force it to shut down.

Power up again, starts fine, runs fine, opens everything fine, seems fine????

about half an hour later, move the mouse, and fittttt, same thing, now its weird!

kill it again, and power on, this time checking power lead before doing so, all Ok there.
this time it only gets as far as windows logon, and am about to contemplate clicking desktop Icon to open outlook, and Fitttttt, same thing.

Now it's really Odd!

So I head off to work, puzzling over it, my wife fires it up later in the morning, and it does same for her? so i came home at lunch time and picked up the box, and took it back to work, plugged it in to test slot at work, and it worked fine for the rest of the day???

Now we are at the annoying stage.

Whats getting to be a long story, shortened, I took it home again, and started from scratch, plugged in bare bones mouse, keyboard (ps2) and monitor, and run again to check it's not a peripheral causing the issue.

Got right through the evening progressively pluging in everything again in stages, and it's running fine, use it for the evening, leave it running over night, come out in the morning, wiggle the mouse to take of screen saver, Fittttttt, same again!

Take it back to work, this time with home keyboard, mouse and monitor, to see if it will do it at work.

It did die same way virtually straight away, so I swapped each component with another, keyboard, mouse in USB, and different monitor, but it still did it after every component change.

Then booted in safe mode,it had a strange split screen that was hard to navigate, so closed it down via windows, and restarted normally, ran fine for the afternoon, did virus scan with AVG8, no issues found, left it running a movie for the afternoon while out of office, when I got back, in hibernate type mode again.

I gave up at this point, and left it there.

Have my work lappie at home tonight, so don't need POS PC!

Any ideas?, I was thinking Power supply, but the PC'S a 7 year old Compaq Presario, so don't want to spend to much on it if I'm going to have to replace it anyway! but dont want to replace whole if it's just a PSU, catch 22 I know!