This morning, the webserver was unexpectedly down for several hours.
When I went online and checked it, I could not connect, so I went to find out what was up. Simply speaking, the lights were on, but nobody was home. Apparently, the PSU fan went some time in the night and let the power supply overheat. I could barely stand to touch the back panel, it was so hot.
I pulled the old server off the rack and stuffed the hard drive from the newer one into it, and we're back in business. Luckily, the drive didn't get crisped in the process.
Unfortunately, this server is bound to be a bit slower until I can build a new one. Here's hoping I won't have to pull out the tertiary machine.