Q: I have forgotten the administrator login for an old macbook. How can I recover it?

I bought a new macbook last year. I put away my old one, a macbook 2009. Now I'd like to use the cd/dvd player in it because the new one doesn't have one. grrrrrrrr. I cannot remember my administrator login. Any way to fix that aside from reinstalling OSX? I was just trying to install elcapitan and it won't do it without the login. Help!