I forget my administator password

This Is My Answer To a Much Older Question, But It Should Solve Your Problem:

You can "reset" the operating system but this will delete any user accounts (but save all the data, unless you have filevault enabled, since it encrypts your data with your password, but new accounts can be created, and if you remember your password later, you can recover the encrypted data) If you can boot into single-user-mode, type these 3 commands, and than reboot the machine, and it will take you to initial setup, though all the old files will still be on the hard disk:

Boot into single user mode by holding "Command"+"S" right after hearing the chime until you see a prompt.

Type These Commands(In This Order):

"fsck -y"

"mount -uw"

"var /rm/com.applesetupdone"

Now reboot the computer.

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