I have an AMD 64 3400+, 1GB Ram and a Geforce 6800 Ultra which I got at the end of 2004.
This is not the first time this problem has happened, but...
When I came to my PC after getting home from college, the monitor's display was all garbled. When I rebooted, I got a "No Signal" message on my monitor, and the light when to amber.
I shut-down the PC, opened the case, cleaned it out, made sure the graphics card was seated properly, closed it up and switched it on. Everything seemed fine, while the system was booting I nudged the tower a bit, to move it back into position. I heard a "click" from inside (like the sound the PC makes when you first boot it up) and it reset...The "No Signal" problem arose again. Had to do the whole "open case, fiddle with wires/check for a loose connection" again.
Once again, it started booting up fine and I moved the tower again. Same problem, same solution.
Third time, I waited until XP had loaded fully before moving the tower and then there were no problems.
I've had this problem before and it seems to sort itself out, meaning that I can still move the tower around while it's booting up and it wont give me the error again. This problem comes and goes but has never been too serious, just throws me into a worry, but I've always resolved it myself.
Any ideas on what could be the cause of it?