I am building a new PC using a gigabyte 939 Dual Channel MB with 2 gigs of Dual Channel DDR ram. I have most of what I need bought, but I bave heard that a lot of devices I use don't have 64 bit drivers yet so can I continual using XP PRO on this PC until enough drivers are available. Also would Media center work on this system?

Simply put YES.
XP Pro will happily work with this setup, but to get the most from it running XP64 would be better. As you have mentioned there are few 64 drivers around, but they are increaseing quickly.
Media Center will also work fine.

Thanks I was not sure. I may run a duo booth until I no lnger need the other as I plan on 2 200 gb sata and 2 120 gb ide drives