My father-in-law bought a computer

Question

My father-in-law bought a computer 2 yrs. ago butthrew out the original box immediately. He was neverable to get it "up and running" (to be able to log on)and went back to using his old one. He gave us this basically new, unused computer but we aren't able tolog on. He said he never logged on either, that therewas a number on box that need to be used to originallyset up password. What can we do? How can we go about setting up first time password?