ok i can help u out
you wont be able to play it
no serious, i've got the alpha version on my pc (yeah i know ....), it runs like 40-50 fps without enemies and 2-3 fps with one enemy (i think this is a alpha version issue, but at least you can shoot at the enemies, i remember i had an unreal 2 alpha 2 years ago or so and if u shot at the enemy the game crashed)
i've got a athlon xp 1,9 , 512 MB RAM and GeForce4 Ti4200, thats pretty good system but i couldn't play the alpha smooth with enemies on the screen, no problem without enemies though, it looks GREAT, a little bit to dark though imho
edit: the gf4 has 64MB RAMand i've got a sb audigy 1