It's the VIA EPIA C3 800MHZ mini-ITX model.
http://www.viaembedded.com/product/epia_v_spec.jsp?motherboardId=141
Performence-wise it's about PR 400 mhz, I would say. I put it in a small black miniITX case, added a Seagate Barracuda 80GB drive, a CD-RW, 512MB of PC 133 RAM (256 is enough), an USB 802.11B wireless adapter. It's super quiet. I use its TV out connecting to my TV, and put it next to my stereo deck in my living room. I have about 70GB of music on it. It's good enough to play VCDs and steam WMP files from Internet and my file server besides being a music server.
Software wise, it dual boots XP and Linux. I use Apache::MP3 and Netjuke as jukebox software on it.
I've had it for over a year now, and I can't say good enough things about it -- it's good at what it's meant to do. If you are looking for a regular desktop machine, there are plenty of altenatives.