Logging into Mac OS X Hidden Administrator Accounts
Every once in a while I need to login to a hidden administrator account on my Mac. It's a simple process after you invest lots of time trying to remember the key combination needed to expose the User Name and Password prompt instead of the usual graphical user account login prompt (which doesn't show the hidden admin accounts of course). Many times I've searched all over the Internet to uncover the secret and never seem to find anything quickly, so I thought I'd document it here for future reference.
Let's assume that you're staring at the usual graphical login prompt. There's a nice little picture to the left of each of your user accounts, but no way to enter a username. If you only have one user account on your Mac, you're already being prompted for the password to that account. If this is the case, hit Esc.
Now you should only see a list of all the user accounts on your Mac, and should not see a password field. Press the down arrow key until you see a gray background behind one of your user accounts. It doesn't matter which one.
Next, press Option-Enter. Your normal graphical login screen should now be replaced with two text entry fields, one for your User Name and one for your Password. Now you can enter the username and password of your hidden administrator account (or any account for that matter). That's it.
Please note that I don't know if the Option-Enter key combination does anything if you don't have any hidden accounts. You'll have to try it for yourself and see.