To delve into on what DH said-
ANY 32-bit OS (XP, Vista, Linux, Mac, you name it) has 4294967296 (2^32) addresses it can allocate to memory. BUT, your other hardware has to also have addresses, so that max amount is lowered by the amount needed by the other hardware components. This address space doesn't reduce the amount of ram on the system but it does reduce the number of addresses the CPU can allocate to memory. This is why some folks can address 2.8GB, others 3.3GB, and someone else 3.8GB.
And just to answer for whoever is about to ask - 64-bit OS's can address 16.8 million terabytes.
Yeh, we tried one of our 4GB machines with 2 SLI'd 1GB GTX285s running under XP32 -hmmmmm.....
DH.. you forgot the most important bit.. after you got Win7 and plugged in those 2 GTX285s, how well does it run Oolite?
Most games have some sort of paddling-pool-and-water-wings beginning to ease you in: Oolite takes the rather more Darwinian approach of heaving you straight into the ocean, often with a brick or two in your pockets for luck. ~ Disembodied