remove the three Phillips screws under the fan closest to the video ports of the card
Lift the fan out(will be attached to a small cord but gets out of the way well) and shim a small cushion under the center circle, between the aluminum cooling fins and the plastic. I used electric tape, rolling it, sticky side in, to form about a 6 layer small square of tape. It shimmed in nicely.
Reassemble and re-install the card into your computer. It should stop the vibration.