That's the big killer. Without the 4Gig Patch (AKA Large Address Aware) your PC, no matter how good it is, will only apply two GB to the game, and it will crash every time.
It comes with BL!TZKR!EG's excellent Front End (along with a bunch of other good stuff, if you want it).
http://www.subsim.com/radioroom/down...o=file&id=4441