School Computer Hacking

My homework due next week is to hack into my school laptop and gain Admin access. The laptop has been "reset" to Windows 7 Professional and there is a username and password requirement when I start the computer (login screen). I got no idea how I'm supposed to do this because I can't even re-install Windows 7 Professional 'cause I get CD-ROM error :/

Any hints/idea's on how to succeed?