Just read about this on The Apple Blog.

Pretty useful information especially for someone in the IT field. Here is the POST

To reset your OS X password without an OS X CD you need to enter terminal and create a new admin account:

  1. Reboot
  2. Hold apple + s down after you hear the chime.
  3. When you get text prompt enter in these terminal commands to create a brand new admin account (hitting return after each line):
    • mount -uw /
    • rm /var/db/.AppleSetupDone
    • shutdown -h now
  4. After rebooting you should have a brand new admin account. When you login as the new admin you can simply delete the old one and you’re good to go again!