I have read about similar video card problems on this site but I think mine is a slightly different issue since I have already tried most of the suggestions posted here. I have an nvidia geforce 9500 GT which I have been using for a while then just one day when I started my pc, I got a black screen right after the windows splash screen. I can hear the windows start-up sound in the background but I couldn't see anything on screen. I restarted and went to safe mode and I can see my screen again. I uninstalled all video drivers, restarted, installed video drivers again, restarted and I'm back to the same problem, black screen. I decided to reformat my hard drive and re-installed windows xp (SP2). Everything seems to be working just fine until I install my nvidia video drivers. Restarted my pc, and it's the black screen again. If I wait a bit, my monitor will say "No Signal". Then my pc restarts. I did the whole process again, this time I tried to install the updated drivers from the nvidia website but I still get the same problem. Your suggestions here is very much appreciated. Thanks!
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I saw the same symptoms; long story short, one of my RAM sticks was the problem. Without that everything was fine, with that stick, by itself or with the other 3, black screen. Ended up with 4 new sticks, also fine.
I will try changing my DIMM but I removed my graphics card and I am only using the onboard video and it's working just fine.