I guess Elfriede, has hit the nail on the head. If I understand correctly you want to test the application on different platforms (operating systems) but want to do it on the same machine (PC) and that too with minimum time spent changing the OS.
Check out the information about Norton Ghost on the web. We have used Norton Ghost extensively. You can switch between different operating systems within no time. This is very vague description of Norton ghost but check out for more. Infact there was a discussion here some times ago about the same topic. Here it is Old Soul in New body