Love this o.s. I was a die-hard XP user, didn't adapt well to Vista at first. Someone told me to try windows 7, and it feels like an unbeatable fit. Got the Professional 64-bit because I'm running 8Gb RAM and if I need to revert to xp-oriented programs, it has "Run in XP mode" capability. Boots, runs and shuts down very quickly on my new SSD. Disk was for OEM with a new COA sticker and unused product key. The license can transfer if I sell my computer to another owner since the copy is OEM and not retail. Got a great deal on this O.S.!