I have a PC that had two HDD. My main with Windows 10 installed which was running fine. The second HDD had an old install of Ubuntu on it. Casually yesterday I booted up the second drive just to see if ubuntu had any new features in the last few years. Once Ubuntu had updated I could no longer boot my Windows HDD properly. I got a message saying "No bootable device".
I physically removed the Ubuntu HDD from the case, but, ubuntu still persisted to show in the BIOS boot selection list. I'm not 100% sure but I think this is the problem.
I have run the windows repair procedure several times but to no effect. I have run bootrec /bootfix from the cmd line that runs in the repair environment as well as /bootmbr. A method I got from YouTube.
I also physically flashed the CMOS on the motherboard with the jumpers in the hope the board would "forget" the ubuntu UEFI, but it was still there.
I've done a fresh install of Windows 10 in a third drive I had laying around, hoping I could resolve the problem with a working OS then swap back later. The fresh install ran about 10% speed for some reason.
Any help at all would be very welcome. I've tried almost every method I can find on the web after a full day of searching but nothing works.