Hi, I have done the following different upgrade routes on different machines. Machine 1: Came with Windows 8 pro, upgraded to 8.1, then multiple insider builds and then 10240. This is still on this build. Its activated but I am not sure if I can do a clean install on it. Its working fine but I'd like to know if its wise to do a clean install as technically I never "reserved a copy" I guess. If I want to not be an insider should I just leave the insider program? Machine 2: Came with Windows 8.1 (not pro), upgraded to the insider build then 10240. The insider build was automatically installed as the non pro version but I used add features to convert it to pro. I got 10240 pro on it as the TH1 update. I then reinstalled using the iso on the MS website as the installation had many quirks with drivers etc. I did not input any key as it was refusing the oem win 8 key. After installation used the change product key in settings and entered the generic Windows 10 pro key (insider key). Windows added features and then after a reboot it had activated Windows 10 pro (even though the machine came with a non pro edition of windows 8 originally) Is this permanent? Did I somehow get a win 10 pro license for it? Machine 3: This machine had no os on it and never had an insider build installed. Installed with no key tried to use the generic key. It got converted to Windows 10 pro but did not activate. Machine 4: This machine came with Xp. Installed a preview build on it, updated to 10240 with windows update. It was activated after this. But tried a clean install on it with the iso and then adding the key, it did the same as Machine 3. Machine 5: Came with Windows 7 oem. Installed Windows 7 Ultimate on it and used slmgr to add the certificate and key for ultimate even though it came with home premium. Upgraded to Windows 10, it is activated. (Is it safe to fresh install on this?) Machine 6: (Virtual machine) Windows 7 with Daz loader, would it activate and work with fresh installs if I same the VM's config after an upgrade to Windows 10? Thanks, and hope you find some of this useful / interesting.