Yep, it has a jump key.
Doom 3 alpha plays nice and slowly on my XP1900+, 1GB DDRAM and Radeon 8500. About 15fps max i think, down to about 5 seconds a frame on high detail 1024*768, lol.
I thought I was going shit myself the first time I played it and something ran up behind me and started battering me. Tis a very atmospheric and moody game!