I've been having trouble getting Canon DSLR drivers working in Windows Vista.
The computer recognizes the cameras (40D and XTi) as "Digital Still Camera", but doesn't get any further. I followed the instructions that came with the cameras (install software, reboot, then plug in camera). I've tried reinstalling the software, disabling antivirus and other running apps, etc. Nothing has worked yet.
I just use a card-reader for transferring files, but I'd like to do some tethered shooting.
I haven't had any problems with using Vista with my cameras. I've used Vista Home basic, and Vista Business with no problems with the drivers, software, or linking the cameras to my laptops. I have done tether shooting using both versions of Vista with my 40D with no problems.
We had problems getting Vista (new laptop) to play nice with my wife's XTI - very similar to what you describe. So I went to the Canon website and got newer versions, or at least those compatible with Vista, of the software (DPP, EOS Utility and ZB) and have had no problems since!