The driver has detected that device \Device\Harddisk1\DR1 has predicted that it will fail. Immediately back up your data and replace your hard disk drive. A failure may be imminent.
This wasn't my first sign, but it was the clearest. A few times now I've had the dreaded "something that was accessing the hard drive inexplicably pauses for a few seconds" glitches. So, time to order a new hard drive.
Hopefully my secondary drive is the one that's failing, because I really don't want to reinstall stuff. I'm pretty sure it is, since "Drive 1" highlights when I click on "Ashley (D:)" in Disk Management. This is the last time I install two identical hard drives, though I was greatly amused at the time for having a hard drive named Mary-Kate and an identical one named Ashley.