Sam Goldwasser writes:

What piezo speaker inside a PC?

Not entirely implausible -- I've encountered a couple of machines with
piezo transducers on the motherboard instead of the regular little
speaker that most machines have. One of them had a speaker as well for
no obvious reason, and I was most annoyed to find that removing the
speaker didn't stop it beeping on power-up...

I've also seen a Promise RAID controller (an SX-6000, I think?) that
had a piezo beeper on the PCI card. Since it beeped every couple of
seconds whenever it was checking or rebuilding the array (which could
take several hours), it fairly quickly got a blob of Blu-Tak wedged
over it to make it a bit quieter.

--
Adam Sampson http://offog.org/