When you want to try out a new application, where do you install it? On you Old System or on your Clean System? Install it first on your Old System. Try it out there. See if it works and if you like the software. If you end up using the application very often, then also install it on your clean system. If you only use it infrequently, leave it on your old system and use it there when you need it.
	Businesses have different terms for these two systems. They call the Old System their Test System and the Clean System they call their Production System. You too can set up a Test System and a Production System on your hard drive using the standard architecture of multiple operating systems. It works like a charm!