Reset the login keychain
For when you cannot find your keychain password
Normally, the keychain password is the same as your login password. If this is not the case, follow these instructions to reset the keychain password. You will lose your saved passwords in the process.
1. Go to Applications -> Utilities -> Keychain Access.
2. Choose Keychain List from the Edit menu.
3. Delete
the "login" keychain.
4. Delete
the keychain file from /Library/Keychains in the user's home folder
The next time
you log in to the account, OS X will prompt you to create a new login keychain and password.
Adapted from
http://docs.info.apple.com/article.html?artnum=301364