Having replaced Siobhan's motherboard, memory, and video card, I thought it might be a good idea to see if the still-working memory and motherboard (replaced because of its reliance on an AGP video card, which are scarce and obsolete) might be useful to upgrade the file server. That server doesn't do anything that needs a video card at all; onboard video is entirely adequate. All it does is serve file shares, a printer share, and a connection for a scanner; run our home automation server HomeSeer; handle our dynamic DNS; and run TVersity to serve multimedia to the PS3, Archos, etc.
So I shut it down, opened it up, and looked at what was inside. The old motherboard also uses AGP (and has nothing in the slot), and a Sempron (not the same socket though), and it had only 1G of RAM though specs on the motherboard said it could handle 2G. I evaluated what was hooked up and convinced myself the replacement motherboard I had in mind had everything needed to replace it, and would fit in the case. Then before I put it back, I decided to swap the memory out to double available memory. Nothing else had been changed, apart from blowing out a lot of dust from the entire system.
Hooked it all back up, turned it on, and there was a nasty burning smell. Shut it down quickly, but it was too late. Subsequent attempts to turn it on, even with the original memory put in, caused the same smell at first, then nothing. No beeps (though there's no speaker for POST) and no flicker of action on the screen. The power supply runs, the fans turn, I even hear the hard drives spin up sometimes, but nothing else.
We can live without the server for a few days. Just means the lights won't turn on and off automatically, we can't print or scan, and no way to stream audio or video (other than from my PC). It's still a bit disheartening. I didn't do anything risky, just looked at it, and swapped out two memory cards, and that's it. This shouldn't've happened. So now I have to scramble to come up with a cheap AM2 CPU. I'm bidding on some on eBay, but I really don't want to put $50 into this so it's soon going to come down to a choice: can I stand to be without the server as long as it takes to pay a reasonable price for a second-tier used CPU that I don't really need to put much demand on anyway?