Further to the previous replies I would suggest trying an older Catalyst
driver rather than the latest offerings. Some of the more recent ones have
proved troublesome if I recall.
I've got 4.8 I think. Or maybe 4.9. Most are available here
http://downloads.guru3d.com/download.php?id=18
For all I've heard, the 4.12 Catalyst drivers are supposed to be the
best "all around" performers on the 9800-pro. There are links to that
version on the guru3d page linked above. Even if you have the .NET
framework installed, though, I'd certainly recommend avoiding the CCC
(Catalyst Control Center) version. I don't know how much better CCC has
gotten, but from all the reports I heard it was a bug ridden, memory
hogging nightmare back in the 4.12 days.
To the OP: if you're going to run any relatively recent games on that
"new" computer, you'll probably want more current drivers than 4.x, as
they will likely have bug fixes, etc. to enable them to run your game(s)
better. Just be careful, as ATI have been known to "break" older cards
with driver releases for the new X-series cards.
If you really care how that card performs, do some research on the
Catalyst forum at Rage3d before choosing a driver version:
http://www.rage3d.com/board/forumdisplay.php?f=59
My $0.02,
Jonathan