jdmismypseudonym

If anyone knows anything about computers, I would appreciate help. I just bought Gears of War. This game's minimum specs are pretty much the same as what I have. It requires 2.0 GHz AMD, 1 GB RAM, NVidia GeForce 6600+. I have 2.33 GHz AMD, 1 GB RAM, NVidia Geforce 6600 GT, so I should be able to run the game at minimum specs. However, there is a problem I ahve been running into for quite awhile. It is most prominent here because this is the heaviest duty game I own, however, it comes into play in most of my games eventually, including WoW, Painkiller, and UT 2K4. The problem is fragments of the screen lighting up bright green and flashing randomly. This begins slowly, but grows to encompass the whole screen before long, and, needless to say, gets in the way of my gaming. It looks like this:
I am sure that something is malfunctioning in my computer, I just want to know what. If anyone could send me a simple: "It looks like you need a new graphics card" or, "it looks like a problem with the RAM or the power supply", I would greatly appreicate it.

EDIT: Thank you all for your opinions. This morning I upgraded both my graphics card and my power supply. (The clerk actually laughed at me when I asked if my current power supply would run the card I was looking at.) Anyway, I picked up a BFG NVidia GeForce 8600 GT OC2. It seems to be doing the job well.