I disagree with Dells being bad computers. For two years doing tech support (among my other jobs) for a mob site, where the computers were abused beyond belief, the only issues I had were 2 bad hard drives and one bad nic card out of 50+ computers in the unit.

As far as an operating system, STAY AWAY from vista. there are major security holes, and there are things Microsquash is putting in the upgrades to the OS that are truly irritating, for example, targeted ads which bypass ad-blocking software, and are based on your web site visits and searches. They are planning on putting this IN the O/S, which means no way to turn it off if they do in fact include it.