I am a happy user of Vista Business x64 for quite a while now... No issues at all, all games running as they should (including the whole Tom Clancy's series up to Endwar which I'm still waiting for to come in my country, Crysis and Crysis Warhead). My rig is: Q6600, 8GB DDR2, RAID10 (4 x 250GB WD), nVIDIA 8800GT Zalman, all on a Gigabyte GA-P35-DS3R powered by a 450W Thermaltake PSU.