bought used and do not know administrator password?

Did you get the original installation discs with it?

Well, you need to be able to boot from the installer disc in order to reset the password.

You may be able to get copies of the originals by calling Apple Customer services with the serial no. of the Mac, otherwise you're going to need a retail installer.

We need to know the model and year to have an idea if Tiger was the original OS or an upgrade, and if the original whether it will boot from a Tiger install disc or a Leopard one.

If you can't log in to find the info, take a look under the stand for model nos. An EMC no. and/or catalogue no. will help.

This worked for me on a MacBook from late 2008

1. boot computer and hold the "apple" key and the "s" key.

2. wait for terminal show

3. release keys

4. type without the quotes: "/sbin/mount -uaw"

5. press enter

6. type without the quotes: "rm /var/db/.applesetupdone

7. press enter

8. type without the quotes: "reboot"

9. press enter

This will let you create a new admin account when you reboot your computer.