weird fan problem

i got my imac g5 (10.4.8) last august, the fans have always been quiet..... until now. now the fans are running all the time and are pretty loud. when i put it to sleep the fans stop but the white light on the front doesnt come on or blink or anything. here's what i did that i think caused the problem:
i had a problem with the video conference in ichat as a lot of people do. i googled it and i found a page that said to reset the smu... i dont know why but that is what it said... anyway, i did (i think).
i turned off my computer, i unplugged everything, i waited 10 seconds, i plugged in the power cord while holding the power button, and then i turned it on again. now my fans and my light are screwed up. everything else seems fine as far as i can tell.

i shut down, unplugged power cord, pressed the power button (with no power cord in), then i put the cord in, then i turned it on and voila! no noise

thanks for the follow up. ill stash that tip in the back of my mind