TYhe file format was NTFS, and yes, I always powered down properly (however, we have frequent power failures). Last night I took the device to a repair facility. We verified that the hard drive itself is bad, and that is the reason for my problems. We removed the Western Digital HD from the device and directly connected it to another machine. The drive is dead. I'm trying to decide whether I will spend the money and send the drive to a data recovery company. Thanks for your help, but it looks like I'll have to replace the unit.