User blog comment:PresidentEden78/Battlefield 3 minimum PC requirements released/@comment-124.182.18.72-20110712105825/@comment-1990578-20110712193301

No, 32-bit OS's can only use technically up to 2.99GB. Having 4GB means you're essentially wasting one whole GB.

Most people don't know this, though, and just throw in an extra GB so there can be four 1GB sticks in both of the dual-slot channels for easiness' sake (as it's technically better to fill all of the channels in a dual-slot/tri-slot setup). If you don't believe me, there's always Google and Wikipedia.