Wes,
In the company we have the desktop version of the Radeon HD 4670 running on Vista 32bit and Vista 64bit with no problems. We also have the FX1700, FX1500, FX3700 in the same environment running with no problems.
I'm not sure if you where refering to the mobility version or the desktop version of the 4670. I haven't tested the desktop 4670 on Windows 7 32/64bit as i'm yet to build those up as test machines yet.
Heath