Hard disk failure is imminent. Please back up your hard disk and have it replaced!
A search turned up quite a few hits, but I thought someone here might be a better source. This message appeared on a brand new WD Blue 1T drive, I'm not sure at what point, but I have tried it in two different computers and it gives the same message. (The drive has three partitions and was restored from an image of another drive, which gave no such message.) One source suggested that it was tied in with smart settings in the BIOS or something, and that it may be a result of my BIOS settings.
In spite of the alarming message which appears at boot, it appears to work normally and three different partitioning programs have displayed the drive and partitions as healthy. It is literally a couple of weeks old at most, and was manufactured within the past two months and has a three-year warranty, but I hate to haul it back if it is my mistake.