If you've got dots on the loading screen before the desktop kicks in (where you get the scrolling green bars in Vista) then you've got a dying graphics card. Either that or you're spectacularly unlucky and you've got a problem with your PC
and the monitor... quite unlikely!
No way of resolving it. It's the memory chips on the graphics card, and they can't be changed by end-users.
You might want to try removing the heatsink and fan assembly on the graphics card and reseating it, just in case the heatsink isn't making full contact with the GPU and/or memory chips, but artefacts on the screen generally point to failing graphics memory.
The fact that those artefacts are on the loading screen shows it's not a software or driver issue as the driver hasn't actually been loaded yet. It's definitely a hardware issue.
The Nvidia software will likely fail to load if it doesn't think there's a supported graphics card in the system, so presumably it's such a serious fault that the software is confused as to what's going on.
The desktop 8800s don't have any known manufacturing problems to my knowledge. There were serious manufacturing issues with the 8000 and 9000 series of mobile parts (and my memory remembers talk about some of the low end 8000 desktop parts, such as the 8200s and 8400s) which cause graphics chip death through overheating, but it doesn't affect your card. Not to say that's not what's happened (an overheated card), but the cause isn't the same manufacturing issue.