did you happen to do the install of 10 with more than just the boot drive connected?
I disconnected my other 500 gb to not get confused. I have my main 500gb ssd for windows, a 250 for games, and a 500 standard hdd for backblaze cloud backup. No other windows anywhere which is why it asking that was very odd indeed, now it doesnt though. Got it all transfering back to the new formatted and detected drive, wasn't what I wanted to have to do but better than a loss. I'm tempted to get new ram but 32gb with 8 sticks I bet ain't cheap. Havent looked at that kinda hardware since I built this system like 4 years ago.