Hard drive panic continues

Last night, I thought I'd lost the computer. Shortly after booting, it really flaked out - it thought it was running on battery, apps weren't behaving properly, it was scary. HDD Health was telling me that my hard drive was at 37°C, which I knew couldn't be right - it starts at 42, normally. So I decided to reboot. A few programs refused to shut down clean, and it took a long time for Windows to finish. Finally, it did.

And then the box wouldn't POST. First, it wouldn't ID the CPU. Then, it got through the CPU, but nothing more. I powered it off and let it cool while I searched for our small boxfan, but came up empty. After about 5 minutes, I checked the various expansion cards, disconnected the secondary hard drive, and booted successfully.

I thought I lost everything last night. A fire has been lit under me to get my backups made more regularly.