Thanks for that guys.
The plot thickens a little, as I made a disk image using the same software and the same drive on another desk top and this one took little more than a couple of hours. (there was less data to back up, but not that much less).

Not sure that leaves me any the wiser as to where the culprit is, though :
- the processor itself, which is performing the operation slowly ? Theoretically it is faster than the 2nd PC
- a rogue command somewhere telling the PC to perform the operation slowly?
(there was nothing else running at the time)
- interference from another programme, like an AV (but surely, that would have wrecked the process altogether?

Ah well, as Buddy once said, I guess it doesn't matter anymore.
If that's how long it takes, then that's the amount of time I'll set aside for it.

BTW, there is a fairly standard and reasonable piece of advice which is to test backup images after they have been made.
But surely, if the test fails you're left with a doorstop. THis is why I've never been brave enough to carry out this kind of test.
Any advice from anyone??

Thanks to all

Marc

Marc's SoundCloud
Marc's YouTube