Okay, to put it simply...
I have XP on my current machine. I'm tempted by the current Windows 7 Upgrade edition deals. I hear that it is possible to use the upgrade edition on XP machines, but you need a clean install....So how does the upgrade part work? For all it knows I could install it on a completely blank system, no?
What about if I have to reinstall later, down the line? How would that work?