low rating ati x1900xt

I just installed Vista 5384.4 (Beta 2, 64-bit edition) on my system. Everything runs fine except for the fact that my brand-new ATI Radeon X1900XT graphics card gets a horribly, horribly low rating in the Windows Performance Rating thing, thus disabling effects like Aero, glass, and Flip3D.
I would figure that my brand new card (512 MB of graphics memory) would be more than enough to handle the rigours of Vista... I've tried not only the default Microsoft drivers, but the ATI Beta drivers as well. Nothing changes. Any help on this subject matter would be greatly appreciated - Aero is a huge reason for changing over to Vista for me!
FYI, the card itself gets a subrating of 2.0, and the 512 MB of attached memory a rating of 1.0. My system is a dual-core 2.8, 2 GB RAM...
Thanks,
MadHatter