You cannot start your MacBook in Single User Mode… because… you’ve lost your Firmware Password – which means you can’t get into your MacBook at all. Right?
If you have the Mac OS X installation DVD
On an Apple computer running the Mac OS X operating system, you can create or change a firmware password. Creating a firmware will allow you to force users to log in when attempting to perform different system functions, like disc booting, safe booting and resetting the computer’s PRAM. As an administrator, you can reset a computer’s firmware password at any time by using the OS X installation disc.
- Insert the Mac OS X installation DVD into your disc drive, restart your computer and then hold down the “C” key as the system reboots.
- Select the language you want to use when the installation DVD finishes loading.
- Go to the “Utilities” menu at the top of the screen and select “Firmware Password Utility.”
- Check the box next to “Require password to change Open Firmware settings.”
- Enter the new password you want to use in the “Password” and “Verify” fields.
- Hit the “OK” button to reset the firmware password and then quit the utility program.
- Restart your computer again. Now when users try to perform firmware functions on the computer, they will be forced to enter the new firmware password.

If you don’t have the Mac OS X installation DVD
So – to get around this problem:
- Click here to download precise visual instructions on removing the MacBook’s SO-DIMM.
- Remove the the MacBook’s SO-DIMM.
- Put the SO-DIMM back into the MacBook.
- Plug the MacBook’s Power cord back in.
- Press the MacBook’s Power button, and then immediately hold down the Apple key, the option key, the P key, and the R key – using both hands, and all four keys down at once, and hold those four keys down, until you “hear” the MacBook chime three times.The “chime” is the noise your MacBook makes whenever it starts up. It may take 30 or 40 seconds between each chime.
- On the third chime, let go of the Apple
key, the option key, the P key, and the R key all at once.
Note! : If you’ve already pulled out the SO-DIMMs, as per the instructions, and put them back in again, there is no need to repeat that process again.
This entire process should erase the Firmware Password you put over your MacBook,
this method no longer works on 2010 & newer macbook pros.