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Sorry, I should have made it clearer. What I did was to add a new 120Gb Seagate drive to the existing 40Gb Seagate drive on the system.
I used a couple of the utilities Seagate provides, one of which I think was called Seatools, to copy the contents of the old C drive to the new drive. The utility then, at my request, made the new drive the C drive and the old drive has become the F drive.
The computer boots from the C drive.
Could this be the cause of the problem and if so, what do I need to do now?