We tend to put together a number of systems for various uses. These uses usually revolve around useful work, definitely not gaming. They're more than adequate for general consumption. The summer 2009 system build consists of:
Build Total: $686.92 and $17 shipping to 20785
(prices as of 9.13.9)
This is meant to be a baseline package that we have tested, built, modified and is currently in use and serving useful purposes. As a reference they have only been tested with XP SP3. Of course your XP SP3 build will need SATA drivers, which complicates this build for the home user, in that case installing Vista shouldn't be any problem whatsoever. Ubuntu and Centos of course install very smoothly on these systems.
The overclocking ability of these machines are remarkable, but their stability is found running stock configurations, though I have had great luck with ASUS's automatic OC settings.
The fall 2009 system will be a corei7.