Assuming you have a legit copy of W7 SP1 or W8.1 with a bunch of apps and want to start with a nice clean copy of W10 to rebuild you apps, will all these scenarios result in about the same clean W10 installation? 1. Format and reinstall a fresh W7 SP1 or W8.1 and do the W10 upgrade. 2. Keep your old W7 SP1 or W8.1 and do the upgrade to W10 and then do a clean ISO re-install of W10. 3. Same as #2 but do a full "leave nothing behind" reset vs a ISO re-install of W10.