As I see it there are two options to you
- Use a VM. This will let the boring process run minimized and it should work fine. Any macro software will work with this solution but they will act like two whole computers and it will use more of the host system's resources (ram, cpu. ect.)
- Use Remote desktop on to the same machine. This gets around all of the resource issues with a vm, but the macro software may not work if the RDP window is minimized (I think it should still work if it is open but in the background). This only works on server versions of windows unless you are willing to replace some of the dll's to allow multiple concurrent logons. (The instructions and dll's will be different for Vista and 7)
Whichever solution works best for you, you should go with that one.
If you do get another screen you can use a macro program to do the work in the same session as you, but I have not seen one that does not steal the focus away (unless it is specifically designed for the program it is controlling like a MMO botting program), so you would not be able to play very fast pace games but simple things like internet browsing would work fine (your mouse-wheel won't though) I do that exact setup my self some times.