This is from Canon (page 29): "Note that there are some cameras that are not supported by and cannot be used with Windows Vista: the EOS-1Ds, EOS-1D, EOS 10D, EOS Digital Rebel/300D DIGITAL, EOS D60 and the EOS D30. Also, while the following cameras are compatible with Windows Vista for 32-bit systems, they are not compatible with Vista for 64-bit systems: the EOS-1D Mark II N, EOS-1Ds Mark II, EOS-1D Mark II, EOS 5D, EOS 20D and the EOS Digital Rebel XT/350D."
I wouldn't hold my breath then waiting for a 64bit driver for the 5D on Windows 7. I've been running Vista x64 since its release and shooting a tethered 5D via a virtual copy of XP. Bit of a PITA, but it works.