I have a software program that is not compatible with Vista which is what I am running right now. I am being told that I could run both operating systems on the same computer by using 2/3 for Vista and 1/3 for XP. Will that work?

Have you tried running the program in compatibility mode? Right click on the executable file for the program and select Properties. Under Compatibility you can select another version of the OS to use. See if that works.

While its certainly possible to create a dual boot machine. I would hesitate to ADD XP to a Vista machine. Instead I would want to install XP first, then ADD Vista as a dual boot.

Another possibility is to setup a Virtual Machine with XP. You can use's Microsoft's VM tool or the free version of VMWare.