Vista 64 or XP 64 can make use of the 8 gig of memory your mother board can
support. With comming updates to Vista and fixes to certain video drivers,
it is possible to benefit from up to 4 gig of memory with a 32 bit version
of Vista; perhaps. Stick with 2 gig until you read that the fix is in and
that it makes a real difference. Soon it may be cost effective to go with
solid state storage which should make a real difference in performance.

Richard