A reinstallation cd is a cd loaded with "stuff" (software) you paid for when you bought the computer. Stuff is programs, including the operating system. So, if you break one of your programs, you should be able to "reinstall" it from the cd. The cd is designed to only work on the computer it was purchased with. Meaning you shouldn't be able to take that cd, and put it on another computer. More than likely the other programs the pc came with, like money programs or games or whatever, did not come with separate cds. So they are all on that one reinstallation cd.