You guys are almost right . It's actually an OEM version of windows 2000. Basically, not a retail version in that it doesn't come with books, manuals or boot disks. it is for shipping with a new pc that is pre-loaded with the OS like Dell's and Gateway's are. Really your not supposed to put it on another computer but what Bill gates doesn't know won't hurt him right? . he makes enough money anyway. Also, if you try to get support from microsoft on an OEM version you have to pay for it. OEM versiions are supported by the manufacturer of the computer i.e. Dell.