I have a 1.6 GHz Athlon XP, 768 MB of DDR ram, and a GeForce 4 TI 4200 128 MB videocard. Doom III runs at about 40 frames per second on average, but when you find an enemy, the shit hits the fan. The game slows down to about 20 frames per second when you fire a gun, and sometimes down to 1 or 2 frames per second when you fire a gun a lot. I sure hope that you can turn down the options a shitlode to make it work on your computer.
The graphics are simply amazing in-game. It looks like a playable Final Fantasy: The Spirits Within. Scary as hell too.
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The part where the monster jumps through the pipes in level 2 is probably the best graphics I've ever seen in a videogame.
-Lasereth