I just realised that I have not upgraded all my licences. I have a Win7 OEM licence. I believe that this is linked to the motherboard and CPU both of which I still have in use. However on that PC I think I did a clean install of Win 8.1 and then 10 based on a non-OEM license. The product ID reported by Belarc does not have OEM in it. So, subject to your advice I plan to: Remove my existing SSD boot disk from the PC and put in a different disk. clean install Win 10 using the OEM product key take an image using macrium reflect put my original SSD back and remove the disk with the original OEM windows At a later time I will use my non-OEM licence on a different PC but am hoping that I don't need to do that today. Q1 Will that secure me an extra licence or will it risk screwing up my non-OEM licence (eg if microsoft link it to my hardware)? Q2 Do I need to register the OEM windows 10 with a different microsoft account? Q3 I have another Win 8 or 8.1 licence that I haven't upgraded but I don't know which is the unused key. I have a variety of Windows 8 and Windows 8.1 keys can I tell which have already been used to support an upgrade to windows 10? Thanks for your advice.