There is no Vista Pro version, so what do you actually have, Business?
If you are talking about doing a double upgrade so you can keep your files, even if it would work, the resulting final install might be unstable and I would not do that. It would be better to buy a new hard drive, install you Vista on it, and use the other one to pull your old files from. But if you want to try, give you exact versions of your previous OSes and maybe someone will know if it is possible.
If you haven't run Vista on your computer, have you checked to see if it is compatible. One of the reasons folks did not accept Vista was because of problems with older hardware and software.