Enable firmware password on osx: This post will show you how to enable the firmware password on osx

firmware passwords will protect your mac from:
booting from a cd or dvd
booting from the diagnostic utility on the install dvd
booting from the network
booting from a different target drive
booting in single user mode
starting in safe mode

to enable the firmware password you need to boot your mac from your install disc [hold ‘c’ during startup]
once the cd has booted select
utilities > firmware password utility

tick the box that says ‘require password to start this computer from another source’

enter your new firmware password