Computer OS help

hey guys so finally i got a decent setup but im having some problems.
i installed xp and it only say 2.5 gigs of ram so i installed the 64 bit version and it saw all 4 great… not i couldnt get any drivers for my network card i saw drivers for it for vista 64 bit.
is vista 64 bit the best way to go?

my current new setup
q6700 2.6ghz
4 gigs of ocz ram 4x1gig
xfx 9800gtx + 512mb
evga 780i mb

any ideas of the best thing to do?