ATI has released a new Catalyst Beta Driver for Windows Vista Beta 2

Product series supported:
Radeon 9500, 9550, 9600, 9650, 9700, 9800, X300, X600, X700, X800, X850
Radeon X1300, X1600, X1800, X1900 series
Mobility Radeon 9550, 9600, 9700, 9800, X300, X600, X700, X800
Mobility Radeon X1300, X1400, X1600, X1800
CrossFire Xpress 3200
Radeon Xpress 200, 200M
FireGL V7350, V7300, V7100, V5100, V5000, V3200, V3100
Mobility FireGL V5200, V5000, V3200, V3100
FireMV 2200 PCIE, FireMV 2400 PCIE

ATI Catalyst Beta Driver for Windows Vista Beta 2