During normal operation or in Safe mode, your computer may play “Fur Elise” or “It’s a Small, Small World” seemingly at random. This is an indication sent to the PC speaker from the computer’s BIOS that the CPU fan is failing or has failed, or that the power supply voltages have drifted out of tolerance. This is a design feature of a detection circuit and system BIOSes developed by Award/Unicore from 1997 on.
The funny thing is, this is SERIOUS. Not a gag. It comes straight from Microsoft’s own site.
I guess printing an error message to the screen was too hard. . .
Update: An anonymous commenter below pointed out that this is not strictly a Windows problem, and would happen on a Linux box, too. My humble apologies to Microsoft. It’s still a funny bug report, though. =)