To reset the password on MAC OS X,
– hold down apple+s key while booting the machine, this will take you to the single user mode
– Mount the file system using , # mount -uw /
– Enter the passwd command with username , #passwd
– reboot the machine
Anyway this will not reset the key chain password, to reset the key chain password:
1. Open Keychain Access, which is in the Utilities folder within the Applications folder.
2. From the Keychain Access menu, choose Preferences.
3. Click Reset My Keychain, which is under the General pane.
4. Authenticate with your account login password.
5. Quit Keychain Access.
6. Restart your computer.
ref : http://support.apple.com/kb/TS1544