Oops, a bit of brain fog there - mixing my drive letters. I should have re-read post #1
Drive C is your local disc of course so, yes, you just need to copy drive D.
In mitigation I can mention that on most Windows systems 'D' is the optical drive and I personally use 'E' etc for my back-up drive or data drive or whatever.
I just dug out and opened an old laptop of my own, running Win10, to see what happened and see if it replicated your issue. On signing on it opened a blue screen dialogue asking my to sign in to my account and then refusing to go on until I did so. If that is what you had then the work round to to click on I/O at bottom right and restart, it will reopen with the regular sign-on screen.
Regarding reinstalling Win10 on your original lap-top. I would suggest trying a totally clean reinstall on a new hard drive. Then you still have all your data on the old disc for the time being. When it is all up and running you can re-use the old disc as a back-up drive.