There are several micro-ATX boards which take an AMD64/Sempron/Turion (socket 754) if you are not tied to the P4.
There are usually other considerations than simply small-footprint. If that's what you want then you probably also want it to be queit and cool because you're not sticking it in the basement out of sight. And will you have discs in it, will you run it with a monitor, etc. --jim
