Sorry about that, I used the wrong term, I should have said 'Scan and Repair'. I was thinking 'diskclean'. Of course, running overnight did not work out, I would not have been able to monitor the progress counter, so I had to postpone to yesterday, March 17. I started the Scan and Repair process at 0800 and it ran until 1545. At 1545 the scan stopped, for a moment or two, the PC screen showed the WIN start up screen, and then immediately the P.C. launched into' Scan and Repair' again. That had me worried, because it looked as if the software system had gone recursive. My concern was 'how do I stop this recursion without severely damaging my software environment?' I let the system run while I tried to formulate a plan of action, eventually, the only reasonable interrupt that I could think of was to let the Scan and Repair process run to completion and to intervene when the WIN start up screen popped up again. To my great relief the second pass of the Scan and Repair process terminated after it had finished its work on the first HDD, removing the need for manual intervention.
My original post about the 'frozen' progress counter was confirmed, it sat there stubbornly indicating '10% complete' during the entire seven and three quarter hour process pass for the three HDD. I followed your process rigorously, yes, including complete disconnect from the primary a.c. supply by the simple expedient of disconnecting the a.c. supply connector, and a one minute wait to allow capacitors in the p.s.u. to discharge fully.
I can confirm that I used my sysadmin account and that 'safe mode with networking' was the mode of operation, also that the wireless communication path was shut off, as indicated by the red cross on the icon.
The P.C. is connected to my DSL gateway and router via a hard wired connection, not WIFI. I consider the wireless link to be less secure than the hard wired connection.
In case you need to know these things, I have included some system information about the P.C. I am using:
HP TouchSmart 310-1125f, 8GB RAM, HP Product number BV551AA#ABA, serial number 4CS1150KP9. AMD Vision c.p.u.
I internal HDD, 2 external HDD via USB 2.
Operating system WIN 10 Home, 64 bit.