|well looking at the amount you have im guessing your running x86 xp on a machine with 4gb ram, while your respective video card is using up the rest.|
Im still guessing however it is something with your drivers. try out omega drivers. a lot of time their not quite as buggy as the official drivers nvidia/ati for certain applications.
However if that still doesnt help please post some info about your system, what game your trying to play, what games actually work etc etc.