Hi guys thanx for your inputs, however, niether of your suggestions applied. I tried plugging into different ports, but the out come was the same. So I switched off the PC and unplugged the HDD. I rebooted the PC, then switched it off again and plugged the HDD back in and rebooted. Bingo, it was recognised.
Phew, that was a scary moment. I keep meaning to do more backups of my data, but I'm sure you know what good intentions are like...perhaps tomorrow. But we all know tomorrow rarely ever comes for fixes. Tomorrows are full of regrets for the fixes we never got around to do.