BTX? Anyone?

It's a Dell OEM motherboard. It's loosely based on ATX, but OEM's like Dell, HP, Compaq etc tended to stray from the standards and do their own thing.
You'll find it difficult to fit in a standard ATX case without getting creative.

I can't tell what model that board came out of, but if its a GX270, be wary because they were notorious for bad caps. Pretty much every one we had at work ended up with bulging caps. The GX280 and later were much better.

I can't tell what model that board came out of, but if its a GX270, be wary because they were notorious for bad caps. Pretty much every one we had at work ended up with bulging caps. The GX280 and later were much better.

The GX280 had just as many problems as the 270, in my experience. The board in the picture is from a Dimension 4300 though. I don't believe those had too many capacitor problems.

But yeah, fitting that in a regular case ain't gonna happen without some serious effort and decent metalworking skill. And even then you'd really still need the motherboard tray it originally came with.

Thanks for the information! It's probably not worth serious effort, so I think I'll test it, and if it works, I'll sell it on eBay. 😀

Even testing it will be a little tricky without the front panel board (which plugs into that small-pitch 34-pin header between the southbridge and piezo beeper), because the power button/LED board piggybacks off a header on that front panel board... I don't know the pinout of the 34-pin header.

I'm going to guess that this pinout will work:
http://www.motherboardpoint.com/796460-post9.html
If I'm wrong and something gets fried, then oh well—it's no big loss.

There's always the "run a screwdriver along the header pins to jump them and see if it powers up" trick. Haven't fried a board...yet. 😉