Could this be the reason behind my inability to login? https://support.microsoft.com/en-us/kb/223188

Oops, I deleted it..................I know, I know.

I never even thought of cloning it onto a spare HDD in a caddy.

Now that I think about it in retrospect, there is an entirely better path to...

I had assumed that the ex-W7 partition onto which W10 had been upgraded had been MBR and so that issue never really arose in my queries. I have never been in the position to choose between the two.

I've moved the upgraded W10 partition to SSD alongside W7 dual-boot. I used EaseUS Partition Master for the cloning but forgot the boot partition behind on HDD. After much fiddling around with...