Video hardware problem

[Animeniax]

First:
Check Connections. Screen/Video Card and Video card in slot.
Check power connections for the video card and mother board. You get my point, if you can check all of these little things, do it

Nvidia card? Nvidia nforce? drivers and bios for the latter.

next is the harddrive... scandisk or better tool to seek for bad sectors.

I doubt the ram could be a problem, a memtest could tell more.

Back to square 1 with a different path: is the PSU ok? hard to tell most of the time. maybe with a cpu+gpu burn you could tell.

This is the stuff you should be checking.