Here is something peculiar that happened. I bought Vista home premium OEM from Newegg just after it came out. I installed and activated it. I used Vista for about 4 months then got tired of it and went back to using XP most of the time. Recently, I built a new computer (different CPU and MB) and bought an OEM copy of XP for it. After playing around with new computer, I thought it would be interesting to install Vista on it just to see how the games looked in Direct X 10. I installed my old OEM copy of Vista on a second partition of the new computer. It installed OK. I was having trouble updating Vista initially, and was getting error messages. I did a repair (upgrade) installation of Vista (without putting in a key) and then downloaded and installed Vista SP1. Things seemed to be working fine. Just for curiosity, I thought I would try to activate Vista on the new machine just to see what happened. To my surprise, it activated using the original key. I checked with the online validation site and it is indeed a valid copy of Vista. So it seems I was able to install the same OEM copy of Vista on two completely different machines, even though it had been previously activated on the first machine. I'm not complaining, but does anyone understand how this could happen?