Hello fellow GOGers,
I need your help. I know it would be better to use some tech forum but I don't post almost nowhere except here and I have seen there are technically gifted people here.
I started my computer today and after loading Windows I have seen desktop for a few seconds and then it was like signal got lost and monitor went black. It repeated all the time.
I was able to boot into Safe mode and into VGA mode but in the VGA it happens after some time too.
In safe mode I tried some things andfinally figured out that when I remove drivers for my graphic card it works then. Still it's not exactly good solution to be without drivers. :-)
I tried to download other drivers (both newer and older). It is better with them but not good. It means it doesn't go black immediately but after some time (ranging from few second to couple minutes).
I have tried few other things from other forums but nothing seems to help so far. Tommorow I'll try to use my graphic card seeing if it happens too. But I had no problems with it so far. I already tried different monitor and it happend too.
I think I forgot some informations but I am really slleepy right now.
It's quite old computer but I'd like to keep it running. I am using GeForce 6600 GT with WinXP.
I am going to bed but I post now to gather some ideas overnight.
Thanks people.

I had a similar issue but my monitor wasn't dropping signal over something basic like desktop itself, it only happened when I ran certain games.

I went through a several month marathon trying to correct the issue and to narrow it down to my findings it mostly has to do with you system overheating.

1. I was using a very old and in suffiicient power supply unit.
2. We don't have a/c in NZ and so the house is quite warm during the summer making the environment hotter for the PC than what it was designed to handle.
3. I was using an old and in sufficient CPU heat sink and fan
4. The heat sink was clogged with six years worth of dust that had never been cleaned out.
5. My drive was a fragmented mess making my system work harder to read files on it.

All of this resulted in draining more power than what my power supply unit could provide and also overheating my system.

Overheating usually results in a lot of mysterious drop reboots.
And pulling electricity from an overtaxed PSU can result in the video card dropping signal to the monitor.

I actually had this very problem with my current card (GTX 465 on Windows 7) and I sure raged out about it; to the point I once pulled the card out of the machine and threw it across the room. No effect. So don't try that.

Anyway, I'm not sure what fixed it, but I had several 'problems' which were: I found I had the RAM's heatsink touching the backside of the graphics card, so I inserted a layer of insulation. I also suspected my PSU was faulty, as combine with the blacking out was a faint 'click' sound from the power pack - so I replaced it. The last thing was overheating; which I reduced by putting an extra fan inside the case and blowing out the dust with a pressurised can of air.

After I did that, it seems, one of those things was causing the problem and I no longer have black-outs

Yeah, here in NZ, the tech that helped not only replaced heat sink and CPU fan with a more modern and stronger one but also added a CPU fan to the inside of the cabinet by the vents. Apparently that second fan actually helps to suck the warm air out of the cabinet.

Its all about the through-flow! Rather than front-to-back, I actually blast the ventilation left-to-right inside my case, as my mobo is mounted on the floor. I also moved my desk later on to a nearby window, so the fans suck in cooler air sluicing of the panes.

Well after days of experimenting, reinstalling, reconfiguring and exchanging of almost all hardware I finally got hold of another graphic gard and voilá it works now. So it seems mine is dead. Do you think it's repairable and is it worth it? There are no apparent signs of some damage and I don't have a too strong faith in abilities of repairmen here.
Thanks for advices, people.
Now I am going to look for some older card to replace it. Propably GeForce 7900GS.

Delete the META-INF folder, FFS!!
/joke

That's what I thought. So off to search some cheap card. And play old games before I get it. Thanks god for Dungeon Keeper, Warcraft II and OpenTTD. :-) I think with my repairs it's long gone. :-)

Yay, I can play Heroes 3! Why do I need graphic card then? You were the most helpful person so I reward you with rep for answer.

Well, thanks...