Look in every shops, I found an athlon 2000+, 512MB RAM, 80GB HDD, crappy video card, for 350EURs. It\'s not a known brand at all, and the plastics arent really nice, but if you just want the specs, you can find very cheap stuff.
Have you thought of those little comps, I\'m not sure of the name, might be barebone or shuttle, they are very small so you can easily move them, you can use low power components in it (it costs more money than normal components, but approximately as much as laptops) and it\'s fully upgradable