Crysis should have at least 2 gigs, but seeing how vista isn't out, we don't know how well it runs with how much ram. For XP, 2 gigs is considered the sweet spot.
Oh and if your ram sucks try an RMA, they have a lifetime warranty.
Opteron 175 + Scythe Infinity
2 gigs corsair XMS DDR 400
XFX geforce 6800 XT
30G Maxtor + 250G Maxtor
"Let's face it, we're not changing the world. We're building a product that helps people buy more crap - and watch porn." -- Seagate CEO Bill Watkins