If it's not POSTing, then it's definitely either the PS or the mobo, and not (or not just) the CPU. If the PS and mobo were fine, it would POST and give you the beep code for "we don't have a working CPU" (five short beeps is standard, but it varies). And if the fans and lights are working, then it's probably not the PS.
Stop beating yourself up, Logan: an overheating CPU has little or no power to damage the mobo. If you've been cleaning the case fan as well as the CPU fan, then you've been doing everything right as far as the motherboard is concerned.
(Though as an aside, I'm kind of surprised you didn't realize there had to be a heatsink (that block of metal fins) between the fan and the CPU. A fan will improve the efficiency of the cooling system, but a heatsink is absolutely essential.)
Stop beating yourself up, Logan: an overheating CPU has little or no power to damage the mobo. If you've been cleaning the case fan as well as the CPU fan, then you've been doing everything right as far as the motherboard is concerned.
(Though as an aside, I'm kind of surprised you didn't realize there had to be a heatsink (that block of metal fins) between the fan and the CPU. A fan will improve the efficiency of the cooling system, but a heatsink is absolutely essential.)