"No Signal" on boot.

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?

what's the model of your mobo and what version is your bios?

Asus K8NE-Delux. Not sure of bios.

a monitor will only show "no signal" when it doesn't get the 5v provided by your
video card/mobo. it stands to reason that this is a hardware problem and not software related.

somewhere, you are losing power. at least enough to trigger the "no signal" display on your monitor.

swapping out a power supply and/or graphics card would greatly aid in the troubleshooting process.

my .02¢

It may be caused by dust in the PSU where you can't get at it easily.

Remove power and see if a vacuum cleaner nozzle can get any dust out. Stop the fan(s) from turning with a pencil or similar so that you don't damage the bearings.

If you are brave enough you could even remove the PSU and open it up to really clean it out. Don't remove the circuit board though, there could be some nasty voltages under the big capacitors.

I've just swapped my PSU under warranty because it would switch off at the slightest knock on the case and also randomly for no apparent reason.
I made sure it was definitely the PSU by holding it out of the case, switching on the system and tapping the PSU before POST beep; it would immediately switch off.
I suppose it's my fault for buying an EZ-Cool in the first place.

You could try this to similarly identify yours as faulty.