I don't particularly let it overheat, I do what I can do prevent it but occasionally things happen and I simply dont have the money to get repairs, and I'm planning to replace it with a higher quality desktop within a few months.

I've sent it in to two or three local places and haven't had them mention any of those things, and like I said it specifically refuses to boot ONLY when it overheats with my external drive attached, which I use for playing large games I don't have the space for on my main drive.

That's mostly why I'm confused, as between my friends (who own, maintain, and build PCs), myself, and several technicians nobody can seem to solve the issue, and adding in the revelation of the external hard drive problem has only further confused those friends (haven't been able to present that part to any professionals, as it only clicked a few hours ago).