How Do I Change My Video Driver?

[Squish]

I have a Radeon 7770. For a while, everything had been working fine. Then I installed a bunch of updates. Now I have really poor performance in a Win7 virtualbox console. I think it's graphics related. Everything performs really well if I RDP into the box instead of using the console.
And Mesa was among the updates. There's no option for changing video drivers in the Hardware Drivers section of System Settings.

Thanks