chkdsk /r was run on the drive. The process took about an hour and a half, 500Gb drive, and there was no output to the monitor so I don't know the result(s).
The drive still will not back up. I have noted, however, that using Beyond Compare to sync subdirectories with external USB media takes much longer than it used to. The process does not fail, it just takes longer to get files off the drive to copy the data. The "timeout" I see in the error dialog on WHS may be caused by this extreme delay. I can't say that it is any one file in particular that is causing the delay.
I'm not sure what is going on here but an upgraded mainboard, Core i7 CPU, RAM, etc., are waiting in the other room to upgrade this computer in the next few days. I shall keep the 500Gb drive but, after the files are copied to the new data drive, a format may be in order.
Turner