Asus has one out called the Terminator. Unfortunately, although they recently updated their P4 version, the Athlon version is limited to PC2100 memory and (per Asus' site) an 1800+ processor. Also, no AGP slot.
http://www.asus.com.tw/desktop/termk7/overview.htm
Given that they just announced the updated P4 a couple of weeks ago (the new one has AGP), I'm hoping they'll come out with a PC2700 Barton version RSN, but so far. . . .
http://usa.asus.com/products/desktop/termp4_533a/overview.HTM
The Athlon K7 Terminator can be had for US$150-ish from NewEgg, which includes case, PS, mobo, a 52X CD-ROM drive (boots Knoppix really fast!), a floppy, and probably a couple of other things I'm forgetting. All you need is a stick of memory, a CPU, and maybe a HD. I figured I could put one together for under $300 -- but I'll wait until they update it. A P4 version would cost me a hundred bucks more, easily, and I wouldn't be able to put an AMD sticker on it.
Oh yeah -- I forgot the modem. It's sold either with or without. But the modem is a winmodem, useless if you're running Linux. Since it has USB2.0 anyway, there's no reason to spend extra for their winmodem card; just get a USB modem instead.
Not much style to the old one, either -- it's a beige box, smaller than usual, but still just a beige box. The updated P4 one is marginally more attractive, but not by much.
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BTW, my roommate has the older Shuttle SB41G2 (I think that's the right designation, not positive tho). It's been working fine lately; however, when he first set it up with Win2K, it was crashing frequently. Turned out to be a bad video driver that came in one of the Microsoft updates -- so stick with the original driver off the Win2K CD if you happen to go that route. No idea whether the driver that comes with WinXP is a good version or not.