Graphics Card RAM (in Vista)

I've just bought a new PC, and want to check that my graphics card (Nvidia 8800GTS) is the 640MB version, not the 320MB. So far I've only been able to verify the model of the card, not it's RAM. There must be a way to do it, but I'm too much of a Vista noob to work it out.

Thanks in advance.

Or, go to Display properties and then Settings.
Hit "Advanced" button and then go to "Adapter" tab. It should list there the basic details of your card.

Also,

Start > Accessories (I think - why did they put that there?) > Run > DXDIAG

Edit, then go to display tab.