I am sure of nothing.
It has been OK for several years.
It was working when I got it.
It was broken after the PCLOS install ..... could not boot Win from the Grub option.
Win still worked ..... but at times it seemed as if attempting to boot it from Grub caused something to go wrong. Repeatedly booting Win from its on drive was always successful.
Attempting to boot it from its own drive after a failed boot by grub caused problems.
I have come full circle in my reasoning, back to suspecting Grub, but unfortunately along the way I have screwed up the Win install also.
The only other option that occurs to me is that the motherboard is failing ....
There were no discs supplied with this PC ..... just the recovery partition.
Now Win is in a constant loop of demanding to be activated but offering no means to do so.