u cud try 3gb of ram but 4 is pointless because 32 bit is wide and won't index all of it as usuable if i remember rite but tbh if 3gb don't work check ur system cos summin must be wrong cos it sounds good. i run a 2ghz dual core comp, 2gb ram and 256mb gfx card and it plays crysis well in pretty good graphics

ur graphics card could be the problem?
ur hard drive? wot is the read speed? cud be a few things really, lol