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!