Doom 3 is scary.
Want to tweak around a bit to get it to look better? Go here.
http://ucguides.savagehelp.com/Doom3/FPSVisuals.htm EDIT: I never made an autoexec.cfg folder, but I've been told that it makes the game run somewhat smoother. Unzipping the files from the pak file and deleting the pak files supposedly do too, virtually making the load times longer. However, it has been reported it does indeed make the game run somewhat smoother. Multiplayer does not work if you delete them, though. I assume you can always just create backups of these files if you want to try.
It is a essential for you to tweak around with image_useCache,
image_cacheMegs, and image_cacheMinK. The game runs so much smoother when you do.
Currently, I only have a 128 mb video card which runs the game perfectly on high settings at 1024 x 768, but I plan on getting a 256 mb video card as soon as possible. Your processor should be up-to-date as well.