I bought a refurb R3 a month ago and have been having a particular issue with it. It came with dual GTS 450 video cards (SLI compatible). I had an issue that whenever I enabled SLI, the computer would go into a power down and reboot loop. I contacted support and they determined that one of the cards was bad. They send two replacement cards along with the SLI cable. I installed them and the machine works fine until I turn it off and back on again. Whenever the machine is turned back on, the computer switches to windows default video drivers and the only way to get video from the cards is to disable and re-enable the video card drivers. I have all of the latest updates for windows as well as the computer (although many of the R3 drivers are close to a year old. Did they stop tech support for the R3?).