Upload & Sell: On
Is your machine already running Mavericks? That's version 10.9. I'm not sure if it's the same as on previous versions, but here's what I found searching online. Or wait and call your guy in the morning.
Step 1: Boot Into the Recovery Partition
To begin the password reset process for the main administrator’s account, you must first shut down your Mac. Once it’s completely off, you’re going to bring up the recovery startup menu by holding the Option key (sometimes marked alt) as you press the power button. Keep holding them until you see several options appear. One of them will be titled “Recovery–10.8”, or “Recovery–10.7” if that’s your version. Use the arrow keys to select it and press Return.
Step 2: Open Terminal
Once the boot sequence has completed successfully, you’ll receive a language preference screen. Once you’ve selected the correct language, proceed to the next screen, where you will find a list of recovery tools. You’re not going to use any of these, but instead click the Utilities menu and select Terminal.
Step 3: Reset The Password
In Terminal, type resetpassword, exactly as I have. This will launch the Reset Password application. From here, select the drive which your operating system is installed on (Macintosh HD by default), choose the user whose password you wish to reset, and fill out the necessary fields. When you’re finished, click Save.