I have 2 licences (CD-Keys). For your Information OEM Keys in Germany are portable (transferable) to another System and are not hardwarebound like in the USA. 1. Windows 7 Starter Key (32 Bit) from an old broken Netbook. (Starter Edition is also eligible to Upgrade as it seems) 2. Windows 7 Home Premium old unused Notebook. I want to install and upgrade them on my Desktop Computer so that i claimed the Windows 10 Update for future use. The thing is I read that you dont get a new CD-Key when you upgraded and the activation is somehow hardwarebound. My Question is if i upgrade with my Desktop these 2 keys (first upgrade --> format --> next) how can i make a clean install for example after a year on another computer. Can you enter in Windows 10 Setup your old Windows 7 Key? (Dont think so) the hardwareID is different too so how does windows 10 know save my activation to use on another computer? Would be the same scenario in the USA if a person wants to upgrade 2 Windows 8.1 RETAIL keys on one pc and then use the same key on another PC with Windows 10 Clean install. So how to preserve your windows 10 activation?