I know as far as laptops go OEMs having been screwing up vista with their custom editions, may be the same with desktops. uninstall all updates (CPanel > remove programs and features > view installed updates). Go here and get the performance, reliability and compatibility updates only, screw the "security" updates and hotfixes, they just break shit
http://www.softwarepatch.com/windows/index.html
See PM as well, that should clear some stuff up.