I'm stuck on this question. I bought a iMac G5 probably about a month ago for $66 off eBay in working condition. I would like to use it more, but the sound of the fan at the bottom that blows air up into the G5 heatsink is unreal. It's all quiet up until I open a program, ex. Spotify. I know the Performance/Power Saver option in System Preferences, even on Power Saver the fans ramp up. So I've stripped the iMac down, cleaned out everything (and also got a cool picture of the back, that'll be below), and it was still bad. I ordered some thermal paste and re-applied it to everything, and while that reduced it, it still bad. I ran the Support Diagnostics and there was nothing wrong with the sensors or fans themselves. So is it time for a new CPU blower or just accept that the G5 iMacs have more trouble than Windows 8? Oh, the cool picture!