Before I begin, I'd like to say thank you to the people here who helped me realize it was indeed a heat problem over just a "logic board" malfunction. Who knows, maybe when G5 processors get old, they start belting out more heat. Heck, my G5 was IDLING at 80°C! That's insane! What's more insane is how useless my once amazing iMac had become. I could no longer type term papers because it would overheat and the automatic shutoff would kick in... bam there goes my paper. All that to say, I finally finished my fan mod on my iMac. It was almost painful to watch my Dremel slice through the clear plastic casing and shred trough the aluminum heat spreader... but it had to be done! Now my gorgeous iMac has some sweet cool blue LED fans on the back that won't let her climb above 50°C! Thats a 30°C drop from my IDLE temp! And thats with me doing several tasks at once. G5 my friend, you have been reborn! It would only be fair to disclose how I did this type of surgery, seeing as there is a lack of detailed steps on the internet. So here it is, enjoy! Step 1: Head to Radio Shack and buy the following: a) 12v DC power supply ($20) b) 2x Thermaltake 80mm blue LED fans ($20pair) Step 2: Then pop over to a hardware store to get the following a) box of butt splice pieces b) a switch (if you want... I like having a switch on the back) Step 3: Test the fans with your DC to make sure they work (and to make sure you know how to wire it all together)... basically, combine the positives from both fans and the negatives from both fans then run them to the DC you got via the butt splice connectors. The switch goes in on the positive wire before the fans... just being thorough. CAUTION CAUTION! Please be careful here! The next steps are irreversible! Only people who know what they're doing or who don't want an oversized pretty paper-weight anymore should continue! Note: This is a good time to remove the RAM from your iMac. You don't want to accidentally slice it while cutting through the casing on your heatsink! Step 4: The gruesome part! Use a cutting tool, preferably a Dremel ($55 from Lowes) to cut an opening around your G5's heatsink. To do this, its best to take out that lower fan unit altogether, which isn't very hard (lift the latch that holds it down). Cut twice, both close to the edges of the whole heat sink unit but be careful not to slice up the copper heatsink. The purpose of all this is to expose the heatsink to the fans you'll be mounting on the back of the case. Step 5: Yes, I'm assuming you know how to take the back off of an iMac. This is where eye skill plays a significant role. You have to determine where in relation to the heatsink to cut a gaping hole in the back of your iMac. If you're good, it will be directly over the heatsink (mine wasn't perfect, but it worked). It took me several hours using my Dremel to finally cut through the plastic (which basically melts out of the way making a mess) and aluminum on the inside of the back cover. Step 6: You should have an exposed heatsink, and a back cover with a gaping hole in it. Next step is to measure out holes to drill for your fan. I used the Dremel for this (stupidly) but it was incredibly hard to control and i ended up making large holes in the plastic just trying to break through the aluminum. I'd recommend clamping the case down and using a real drill with a bit that can cut through metal pretty easily. Step 7: Mount your fans! I only used 4 screws, due in part because I couldn't stand working with my Dremel anymore. To keep the fans together in the middle, I just zip-tied them... easy, and it works. To clean up the sharp edges on the aluminum and heat sink case, just use the sander tool that comes with the Dremel. Step 8: Test your fan once again! If you installed a switch with it, make sure its working. Put the case back together, make sure everything fits and is not in the way (screw ends from the fans) and close it up. Plug in your stuff as usual, and turn on the fans before you turn on your comp. There ya go! Hopefully your saturday isn't completely wasted, because now you have an iMac G5 that doesn't feel like quitting on you because he's dying of heat stroke! Let me know what you thought of my method and if i should have made any improvements! Not sure if the site allows it, but I can post some sweet pictures of my mod. The iMac truly looks sweet with blue LED fans on the back of it!