I use Vista 64 and have never crashed outside of some initial sound card driver issues. While I do not run more then one WOW instance on my pc at a time I frequently play WOW and LOTRO at the same time with one being displayed on its own monitor.

Core 2 Duo 6700
4gig ram -Crucial Balistix
Seagate Baracuda 7200.10 drives x two in a stripe.
BFG 768meg 8800GTX OC2 Edition
Creative Xifi Pro Gamer Fatal1ty Edition