[Update 5/5/2009] The new location for ATI Catalyst Driver for Windows 7 is here.
I did some benchmark testing comparing 3D performance under XP and Windows 7. I was quite dissapointed at how poorly the 3D performs under Windows 7. I set out to find some other drivers and I came across this official beta driver from ATI(AMD). The packages supports these following cards:
Here is the download page.
Let me know if this works for you.