Vista is nothing if not messy about compatibility with older programs. Don't ask how much grief I had getting AutoCAD to run on a co-worker's Vista box or how much of a pain it was not to be able to get my HVAC load calculation program to run under Vista beta.

If Vista doesn't work with the update, the most likely option is to find a non-Vista PC. I'm hanging onto my wife's old Dell laptop (running WinME, ack) largely for this sort of stuff.