Welcome to MobileRead, mgmharry!
I can't directly answer your question, as I'm not using Vista (my plan is to wait 'til they're working on the replacement to install it -- that's when MS OSs tend to get stable
However, I can offer a couple of things to try that have come up before.
BD won't work in Vista from the "My Programs" directory. Also it needs to be installed with full Admin privileges.
You may also find useful the ongoing discussion of BD & Vista located here