You need to know mac os version and how old is your macbook? You can boot any mac from cd and reset password. If your mac have 10.7 or 10.8 then you do not need CD and instead can use Recovery partition. The process of resetting password is little bit different in 10.7 as in 10.6.
If a macbook is password protected and the password is not known can I put OS x 10.6.3 in CD slot and start up from there? If yes, will it reinstall so I don't have to start from the CD all the time?