The HP xw6200 is a brilliant dual-3.6Ghz Xeon workstation that is the baby brother of the xw8200 which was Avid's workstation of choice for a couple of years until the Z800 came out in 2010. It's still a powerhouse and re-furb places like Tier-1 knocks them out for a bit more than £100. Given how pokey they are and how well build HP made them (you got quality when you paid >£2k for a PC in 2010!) I often recommend them to friends.
Anyhow - couple of gotchas;
- Make sure you re-set the BIOS to disable the onboard SATA RAID controller or when you install Windows 7 SP1 you re-boot and get a corrupt boot partition and have to start all over again!
- The graphics card is an nVidia Quadro4 400NVS - a quad-monitor CAD/NLE display adaptor that has no Windows 7 driver!
Still, an excellent deal if you're willing to put in the time to sort it out.