Kerbal Space Program is not exactly the most optimized game I've ever run. It has gorgeous graphics, lets you fly to other planets, and has relatively good physics... but my five year old laptop, an XPS M1330 Dell (which already had issues with overheating) basically looks at that game and says "NOPE."
It started to overheat to the point where the outer surface was actually painful to the touch. The overheating had already been starting, even before I began playing KSP; however, it had never actually been so hot that touching the casing was painful.
At this point, I immediately closed KSP (three minutes) and turned the laptop off. After waiting for some time for it to leave the DESKTOP (seven minutes, roughly), I decided that the computer was frozen and did a hard power cycle. I'm not entirely sure whether it was the overheating or the hard shutdown, but one or the other corrupted the registry and at that point it wouldn't start at all.
Unfortunately, despite the fact that this was the only computer I have ever had which hadn't died permanently within a year, I apparently never learned my lesson to always, always, ALWAYS have a backup. As a result, I don't have a backup from recently enough that it's worth losing some recent files to maintain my system settings (despite the fact that said settings include, oh, vital things for various programs).
So although I haven't actually lost any files, I am currently computer-free and as a result cannot play Blockland until I get another one, and likely won't be posting anywhere nearly as much because typing on an iPod is a pain in the ass that cannot be described.