My PC all of a sudden rebooted and my monitor displayed a No Signal message. The PC couldnt seem to boot anywhere, no whirring or flashing of lights. Just kind of stood there. Because I couldnt see the display. My tower has a see-through side and I could see that the fans and lights of the 3d card weren't moving.
I didn't know what was happening so I turned off the power and disconnected the monitor cables from the video card (Geforce 6800 Ultra). I turned the power back on and the 3d card seemed to be spinning fine, the PC seemed to be rebooting. I powered down again and then dusted out the case, especially the jacks of the 3d card incase there was a dust problem somewhere. I plugged the monitor back in and switched on, got a display...PC booting up, then suddenly it just makes a noise as if it's restarting again, display goes blank and 3d card powers down.
Once again, powered down the system, unplugged the cable, plugged it back in and powered up again. Things seemed fine, booted into Windows, then I gave the tower a nudge by mistake...Very, very slight but it caused the 3D card to short-circuit (is that what was happening?) again.
Once again, powered down. I don't know much about PC hardware other than just cleaning a case with all the components still installed, so I just kind of fiddled with all the wiring and molex cables, just pushing them into their connectors more firmly and tweezing the wires with my fingers.
Plugged back the monitor, powered up and now things to be fine (I didn't bother with the secondary monitor, in case it gave problems.) It seems that there's something on the 3D card, or another component that was very sensitive to movement, I'm not sure which part it was, but when the 3D card didn't power up properly (just gave a flicker, then spun down) the CPU fan also seemed to power down.
Sometimes I've had a hard reboot from knocking the back of the cable, pushing the 3D Card and making it shift a bit in the motherboard, which I guess causes the short...It just reboots, but never gave me the problems it did now.
I'm taking it in tomorrow to get it checked out, but what do you think the problem is? Is the 3D Card dying or is just the wiring thats loose somewhere on the system that causes a short when there's enough movement to break a connection?