Either already tried or subsequently tried all the above except for the Nuke and the Easus CDs
. Easus running from a separate disk on same machine, so don't think the CD would make any difference, and by the time I got to Nuke, too frustrated
Diskpart locked up on clean - no error message, just sat there for two (2) hours, all my patience could take.
The disk has been the primary drive in this box for couple of years, so sector size shouldn't be a problem.
I tried to manually delete stuff after diskpart locked up, that's why I mentioned the non-deletable directories.
Yes, I did remember to rewire so that the boot disk is disk 0. But everything seemed to point to having an MBR on the now disk 1, and stuff was choking on it ... not something I remember having encountered in the past, but I suppose that could be reasonable.
Have a friend that dismantles HDs and recovers data onto CD/DVD disks for a living. Called him. He's pretty certain it's a problem with the drive, but wants to look at it, so I yanked the damned thing and shipped it to him. Ordered a new 1T drive, same designation, WDC WD1001FALS-00J7B1 ... well, OK, not identical, but same class of disk. Sorry for the furor, but 'twould seem this was another hardware glitch disguised as software bobbles.