Thanks for all the humour guys!
The good news is.... it wasn't the boot drive that died, that's one of those Solid State thingies, and it boots in a flash
The bad news is... the drive that is dying is a 3TB Seagate, so there's a LOT of stuff on it (including Elite Dangerous.....) . Got my fingers crossed waiting for the new drive to arrive.
Meanwhile, it's a trauma everytime I boot up .... sometime the drive is there in the Explorer list, sometimes not....
Thinking of just leaving the computer switched on for a few days till I'm ready for the surgery....