Admin password

I’m a new IT Admin and the previous admin used a username and password that don’t have on a machine that I need to log in on as Admin. Is there a way to change the admin password in NT if you don’t know what the password is? Also there is a system here with a BIOS password that an employee put on before they left. Is there a way I can remove that? It has left the system unusable. Thanks for your help.