This is weird.

Last night, after a little web surfing, I shut down my home desktop and went to bed. This morning, when I went to turn on the desktop, I noticed that the CD drive tray was out. When I turned on the machine, it wouldn't boot. I checked the BIOS and discovered that the boot drive had been changed from the drive with the operating system to one of the data drives.

Needless to say, I hadn't made any changes to the BIOS.

I changed the boot drive designation back to the correct drive and the machine booted and ran fine.

Ghosts? Poltergeist? A sentient computer?