This is a new one one me... here are the symptoms:
-Res stuck at 640x480 - no other options recognized -seems stable at this res though, doesn't crash. when it tries to load at full res the graphics degrade bit by bit until it goes all black, over the course of about a min and it doesn't ever make it to the windows chime.
screen is glitchy, even through bios. there are broken lines all over the screen that make it even harder to see anything.
must be stuck at 8 bit colors or something.
- unstable: it took maybe a dozen restarts and two windows repair sessions until it finally doesn't crash as soon as windows starts.
Other notes - a few days ago the screen was black and wouldn't come back from hibernate so I restarted, it then did everything i mentioned above but it went back to normal after a couple more restarts. stayed that way for a few days and now nothing seems to help.
did full windows update plus updating from nvidia
Even bios is ridden with bars and glitchy looks but the very strange thing to me is that the splash screen prior to windows load (the one with the pretty orbs that make the win logo) look perfect without fail... why is it untouched and everything else bad.
Device manager says - Windows has stopped this device because it has reported problems. (Code 43)
NVIDIA Geforce 8800 Ultra
Win 7 x64
Intel Core 2 Extreme X9650 3GHZ OC @ 3.33GHZ
Intel SSD Hard Drive
Two good monitors so I can be confident it's not the display
I've been able to find similar cases online concerning code 43. Some report vertical colored lines/artifacts, and a few with horizontal grey/white lines/artifacts like how mine are. Haven't seen any working fixes except one guy who put his gfx card in the oven? wtf..
It would seem to be a lost cause except that the splash screen looks like perfect resolution and color and no artifacts. Before and after that however... No good.
Yes, everything about those symptoms mean a dying card. The best way to test it is asking a friend to borrow his graphics card from their computer that is known to work and testing it in your rig. If his card works fine, then its your card.
Oh and putting it in the oven is a brilliant fix. You have to remove everything that is plastic from the card (so they don't melt). Put it on a baking tray in an oven set to about 220 degrees Celsius. This melts the solder in all the connections on the PCB which will ultimately fix any broken solder connections that could be causing issues. It's only to be taken as a last ditch effort though, only do it if the only other option is binning your card and getting a new one.