My parents have an older 20-inch white Intel iMac that has run great through the years. But about a week ago it just started spinning the CPU fans up to 3500-4000 RPMs and it won't bring them back down. Istat shows that the CPU temp is around 90 degrees and the computer remains cool to the touch. So it isn't overheating. My parents keep it off most of the time because they don't want to ruin it, but they're planning on using it in their business they're trying to start up. We've done some web searches and nothing seems to fix it. Any suggestions here?