Locked out of Admin account. Password lost. Need to reformat.

Hello,
I'm trying to reformat a computer at my work place all of us in the store don't know the admin account password, as a manager from years ago set the password and told no one. We are stuck on the limited access account and using safe mode and running "control userpasswords2" doesn't work because it asks me for an admin password before I can continue to reset passwords forgotten.