I'm on the verge of upgrading. I've just not formatted for a couple of years and currently have a lot of little programs that will be a pain to redownload and setup.
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I've never done a fresh install for that very reason. I always install over the top. Never had a problem doing it this way. Its okay some people say its best to do a fresh install but when you have got it setup just the way you like it its a PITA to setup again.
I had Win 8.1 so going to 10 has not been that much of a boon.