you cannot use the newest drivers with xp64bit, but you can use older ones
. the ones that are made for 2000hd, 3000hd.
you will actually miss a lot of open gl shaders and other features like widi and so on.
and there is a difference in performance between xp and win 7/8 , i would say a huge one, regarding multi-tasking for example.
if you have such a new cpu, i would not recommend xp64 bit anymore, it is a huge performance loss. 3rd gen. intel is the last officially supported processor generation for xp 64bit.