This is bizarre. I re-booted 4/5 times and got the SMART error every time, with the F1 to resume bit. Looked in SpeedFan to see the SMART report which said the spin-up time was excessive, drive fitness was 0% - back up and get it replaced. OK, I thought I'd download the Samsung HDD utility to get a report for the RMA...
Ran the HDD utility from DOS and again - it said the SMART record for the spin-up time was excessive but it passed all other tests. The utility also tested the spin-up at the time (as well as looking at the SMART record) and said it was OK!
Puzzled, I re-booted the machine again into Windows... No errors, and now the SMART record in SpeedFan says the the disk is OK, and the spin-up parameter is back to 100% from 0%.
So it looks to me like the Samsung utility has reset the SMART record? and I have no idea if this disk is stuffed or not...