I personally get a big kick out of ultra-small form factor computers. In my opinion there is absolutely no reason for computers to take up the sheer bulk they do these days, especially with the current technology that's available.
My box is a standard cheapo $25.00 ATX case. I built the computer myself and put all the things I needed in it and so on. The only thing I don't like it the sheer mass of it. Too damn big. I would rather prefer something less than half its size.
For Mac's, there is the Mac Mini - so even the big guys are starting to realize that we don't need these big honkin' computers any longer. Mac also has their all-in-one iMac G5 which includes the computer built-in to the monitor itself. Slick.
For stuff even smaller there are Weeny PC's. These are computers about the size of a Rubik's Cube or smaller. Digression: Check out the Rubik's Web Site. Neat stuff. Take a trip down amnesia lane. (grin)
What I want to do eventually is build one of these ultra-small computers with absolutely no moving parts. This means no moving disk drives or optical drives and no fans. It this possible? Just about.
1) Mini-ITX motherboards are available right now that are "fanless" because they don't run that hot. And yes it will run Windows XP with no problems at all. That's been proven time and time again. So that takes care of the CPU fan noise.
2) It is possible right now to boot from a USB hard drive? Yes. That takes care of the hard drive noise. USB's are obviously silent.
3) There is such a thing as a small fanless power supply, however it needs a 12V source. More or less this means the PSU is meant for an automotive application. Cars use a 12V battery.
Sidenote: I am still searching for a small fanless PSU that will use standard 110v home current. It probably exists already, but I still haven't found it. The search continues. There is a large 300w fanless PSU, but it's too damn big.
Here are some computers built that I think are just plain awesome. You'll probably get a kick out of them too. Bear in mind that this is the future of computing. Style will eventually come into play with all computers - you watch. It's damn close. Mac tried it earlier with the colored iMac's - but they were just a little too ahead of their time.
Commodore 64 933MHz PC (if it only had a number pad and all the "F" keys....)
..and last but not least, my favorite: