It's not a stupid question, it's quite a pertinent question, in fact.
That was almost a big word, wasn't it? (pertinent)
I've tried to do that thing many times.
It's never, ever, worked completely successfully. It may appear to have worked initially, but in my experience, you'll encounter problems later, along the way.
Best option is to back up what you can (don't forget e-mail addresses and saved game folders) and do a fresh install.
Sorry, but that be the truth