[birbear]

the problem is the noise is random... right now for the past hour, the system has been humming along like normal.

This afternoon, it sounded like a ghost was haunting it.

[TheOtherOne]

Before they get here, I am having the same problem on my old MAC G4. It humms fine and then, like a bad dinner, it starts growling and I put it to sleep. I think it is the power supply, since it has basically been running non-stop for almost 3 years. (Yeah, I know a mac plug, but it has with maybe 50 restarts in 3 years!).

I mainly use a laptop now, but I may replace the power supply on the G4 as the noise is getting creepy.