Wow. Since I got my computer, most games have been no problem. Half-life 2 and even Doom work resonably well at high-quality, using 1280x1024 or sometimes 1024x768 resolutions.
Quake 4 I have to run at 800x600, and I'm thinking of lowering that to 640x480 to get rid of the lag. Yes it's that crazy. When you set it to Ultra Quality, a warning comes up saying that over 500 megs of textures must be loaded and that this setting is not recommended for anyone.
Crazy shit.