A few months ago I took my computer into a repair shop and it ended up that a new copy of Windows 8.1 had to be installed, so they took care of that. Now the problem is that recently I tried to install Windows 10 and wasn't able to. I later found that my copy of Windows 8.1 was not activated and that could be a reason why I'm unable to install Windows 10. Now on the side of my computer is a Product Key code for Windows 8.1. I tried to use it to activate the copy of Windows that got installed at the repair shop and it didn't work. I know that I have a Windows 8.1 installation disc that came with this PC originally and the product key did work on that copy. So the main questions I have are the following: Is it possible to install Windows 8.1 from that disc while already on a copy of Windows 8.1? And will the Product Key meant for the original disc copy of Windows 8.1 be able to activate that copy again?