I actually registered primarily to thank another user (lordloss). My TI-89 Titanium wasn't responding to anything. Putting in batteries turned it on, but then it'd be locked up. I tried all the tips and tricks (key combinations, etc.), but it wasn't recognized by Windows to send new firmware and generally seemed unresponsive after initially turning on. Google brought me to this thread: https://www.physicsforums.com/threads/frozen-ti-89.410702/ I had tried everything else, so I figured why not? It's a hot day (around 91 f), so I took out all of the batteries and left it in my car for about 2 hours. I just got it out. It was hot, but not too hot to touch. I waited a couple of minutes for it to cool down and gave it a try. It works! Seems good as new. I would assume the chances of it croaking on me are higher than with a brand new one, but hey, I already owned this one. Anyway, as for me otherwise, finding this forum is timely. I'm taking engineering physics labs to supplement AP Physics C exam credits. I work for an electrical engineering company and want to eventually be an EE myself (currently a tech).