I have to aggree with zainnab. I just completed assembling my new PC and installed Vista Home Premium 64B with SP1
Asus Rampage Formula X48 chipset
Intel Core 2 Duo E8500
8GB (4x 2GB) Corsair Dominator DDR2 1066Mhz
2x 750GB Samsung Spinpoint F1 7200RPM 32MB cache
Asus 9800GX2 - TOP version
I installed Vista 64B and drivers without ANY problem. After that I decided to give WoW a go by installing it. Many forums reported it was best not to install the game but do a copy to the x86 folder of the entire WoW folder. Thats why I decided to check it out myself. I ran into no problems at all. It installed perfect, the patches downloaded in the beginning realy slow but after a while they were fast (had same prob with windows XP in that matter).
I went to Nagrand with all settings to maximum with a resolution of 1680x1050 on my 20" NEC Multisync 20WGX² Pro.
While flying I had 101 FPS and 29ms
When standing still I had 143 FPS and 31ms
I guess the problems some of you are experiencing are settings or system dependant. I know it's not fun to hear but Windows Vista is designed for a more updated system. In paticular the amount of memory is realy important. n my opinion I would gofor it with less then 4GB of mem.