Hello everyone. I recently purchased a used iMAC 24" Mid 2007 for my son to play on. After about a week it crashed. Soooo......being a PC tech I decided to take a crack at it. Well I was in familiar territory for sure as poked around. It looked like some fumble fingers had been in there before me. After all the hipe about how clean the machine was and all the upgrades!! REALLY!!! Total mess. Now is the time where I include all the YouTube and instructional I reviewed in this text. I reviewed many of them during my diagnosis. Could not, would not get the AHT to work. Tried alot of personal work arounds to fix the issue, but no luck. So after I tried the basic fixes for a now slow system that boots to desktop but won't open any programs, here is what happened. Overheating issue?? Don't know yet. Sooo I cleaned up all the fans and inside. After some back and fourth, I finally noticed the following: Broken screw posts. (now some cards/boards are floppy). Inside was filthy. I bought one stick of ram to use as a ram check. Ram ok!!. Hardrive removed and gutted, then checked. Looked new, HDD OK!! So now....CPU was missing a screw!!! Are you kidding me!! WHAT A NUBE!! But most important! I read several articles on OVERHEATING. What I noticed was that the TIN FOIL at the bottom of the case up top was curved up. After I thought about it........This is what is causing the heat to spike and overheat the insides. The hot air is supposed to flow through the power supply PROCESSING units fins. But it doesn't. The curled tin foil had come unglued, therefore, blocking all the hot air and just keeping it inside with no escape. It's funny I never saw anyone catch this(although Im sure someone has somewhere). The escape hot air ports on the upper back of the case are funky to begin with. So one slight alteration .......and boom overheating. Already re-glued and noticed some coolness. Found no pinholes on the GPU sinks. With the CPU missing a screw the thermal setup is comprimised...no wonder it was acting weird. Soooo....I will do a full tune-up most of which is done, inspect all the capacitors and anything else that looks out of wack. Hopefully My son will have a new toy soon!!! First shot at a iMac....wish me luck!! So far so good. If the new K-pro 4 & 5 paste up doesn't work, and all the normal spot checks have passed, can anyone provide any additional possibilities? Remember all normal spot checks are ok, (HDD,RAM, OS USB, Thermal paste, Overheating). Also I flipped the iMac on its back hiked up the screen and blew cold air into the center while I was loading the OS (Mavericks) onto the system. System was cool throughout. My goal was to try the SMC Fan Control software to set the fans according to all the other posts and get the resolve that way, but the other issues popped up during my last inspection. OS worked fine on other iMacs including this one until crash time, which was about a week . Any ideas are welcomed. This was a fun one!!! Thank you so much.