I know this is an old thread but the problem is an intel chip in the machine that won't recognise memory beyond 4 gigs. Further, the memory on your video card counts. So, with 4 gigs of RAM and 1 gig on your video card, only 3 gigs of RAM will be usable. That comes straight from Alienware's tech department. It sucks, but that's the way it is. It's like Alienware thought no one would be interested in using the 64 bit operating systems that were availabled when they built the computer.