Graphics problems after XP update

I'm running XP under PD6. I hadn't update XP in a while, so I decided to do that. There were about 175 updates, both critical and not (let's say I hadn't updated in QUITE a while). Now, whether related to those updates or not, I'm having graphics problems.

For example, running RealFlight G5.5, a RC Flight Simulator. I'd frequently run it before, but now it says, "Your video card is not able to render 3D images...." I have similar problems with other programs. How can I fix that?

BTW, I did reinstall Parallels Tools.

Thanks!