Its not the hardware.

There isnt enough info there to really help yeh.

have yeh set maxbkfps maxfps ?

have yeh set cpu affinity?

what res are yeh running at?

have yeh setup vista for performance?

are yeh loading from separate installs?

what addon are yeh running? are yeh running addon on all instance of wow? some addons are considerably more resource intensive.

Yeh have the latest drivers installed for yer hardware?

Have yeh minimized the amount of services running in vista?