Just to throw my 2 cents in, I use an AMD athlon 1ghz, with a via chipset, on a gigabyte motherboard. with a geforce 2 video card, everything linux I try to run works great, and usually everything is detected out of the box.
sometimes have to upgrade the video drivers, but if you are using the box for a file server then this prolly won't be necessary. I've also heard good things about the via motherboards. try an AMD/via combo, you should have a system that won't have to be shutdown for a long time. even just running a liveCD.