Kbird said:
did you google the BSOD numbers ? it's unlikely you are the 1st one with that Code , so worth a search.

installing a BlueScreen Viewer like below may help identify the issue

Blue screen of death (STOP error) information in dump files.

you maybe right , it may be easier to do a factory reestore and start again , especially now the Win10 Anniv. Update is here , which is a massive download in itself.

Thanks Kbird, the culprit for the BSOD was a 128GB flash drive that I had left plugged in for backup, it had always been temperamental, I had to jiggle it around to get it to work.
I changed the resolution to 1366x768 but it didn't make any difference, so I went ahead with the small dialog boxes & the magnifying glass & lo & behold it went pretty smoothly & I successfully installed W.8.1 on the partition. I didn't expect to get all my apps back, but they were all there, so I'm very happy. The thing I mainly learned was that when installing from a bootable device, it's better to execute it from the File Explorer: Bootable Flash Drive>Sources>Setup.exe file. I thank everybody very much for your advice & patience.