It has to be the drivers. I have the EXACT same thing that you do there apart from i have 1.5GB of RAM. Mine runs HL2 and Dark messiah on medium settings with great frame rates so i should think that you would be able to play WoW perfectly.
What kind of internet connection do you have ATM? If its a high speed one then i would go to
The driver support page and download a later driver.
Oh and how much of your RAM are you allowing your graphics to have?
Spengo
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