I recently ran into a small problem with installing OS X updates when I realized that without the Administrator password I could not install the available OS X 10.3.8 update.
The work around from a Google Group posting was to reset the Administrator password. Below are the steps I followed:
1. Boot your computer using the Mac OS X Installer CD. (Note: You can force a CD ROM boot by holding down the C key during restart.)
2. At the Installer screen, select Reset Password from the Installer menu
3. Select the Mac OS X volume which contains the password you wish to change.
4. After selecting the Mac OS X volume, click on the popup menu for the user that you want to reset the password to.
5. Once you have selected the user type in the new password and click on the Save button.
7. After clicking on the Save button quit the Reset Password application which will bring you back to the Installer screen.
8. Select Quit Installer for the Installer menu.