PASSWORD HELP

I am trying to install new OS. I'm getting this: "In order to continue installing OS X, you need to login as an adminsitrator. Type your password to allow install OS X... to make changes." Then there's a place for my name (not username, but my actual name) and password. So not my apple ID, and not my usual password. Instead, some password that I set nearly ten years ago when I got this amazingly still working thing and don't remember at all. The hint is no longer helpful either, but I obviously thought I was really clever at the time. What the ****!? What do I do?