It's between 2 and about 3.25GB that's usable, it depends on the system. However I don't think 32bit vista suffers from this.you can't even utilize more than 2GB unless you're running a 64bit OS.
if you want to spend you money you could try buying a physics card. Sort of a sidekick for your videocard.
or buy some new quiet fans
or get a new quiet cpu cooler
ROFL ahaha, never but never ever buy an stupid physics graphic card cuz they aren't worth the money and they don't have a use in most game you would be wasting money for nothing.
And I don't know why!!BTW, this thread had nothing to do with a 8800 GTX