A buddy of mine loaned me his copy of FEAR, and I've been trying to find some ideal settings for my hardware, but it's been a bit of a struggle. Hardware is as follows:

A64 2800+ (S754) @ 2.2ghz
1.5gb RAM (155mhz due to OC and 1GB being PC2700)
AIW X800XL 256mb
Realtek onboard sound

Any idea what res the above can do? I'm currently at 800x600, but it gets choppy at times. Also, what settings impact the game the most? I'd like to increase the res at the sake of detail, but I'm not sure where I should scrimp the most. Think the onboard sound is hurting me pretty bad?