I've loaded a heck of a lot of programs from the days of XP and long before, onto Vista, and never had a problem like this. One or two have refused to work, but I have managed to sort them, even spending a whole afternoon in regedit with one of them. (all the registered file paths were wrong).
If you could give an example of the programs it might help.
When installing it's a good idea to right click on the setup file and choose "Run as Administrator." if you have UAC turned on.