Ever since I got my G5 almost a year ago, the hard drive has been really loud. Like 486-style loud. You know, a lot of clicking and banging. It didn't like a failing drive, just loud. Since my warranty is almost up, I decided I'd better take it in for service.
I formatted drive, writing zeroes (I don't trust the guys at the shop but it's the only one in my area) to it. Lo and behold, the drive is now quiet like it should be. The PS chirp is gone too as an added bonus. The PS whine is still there but I guess I will live with it.