Q: i lost my mac pro password

Welcome to the Apple Support Communities

http://discussions.apple.com/docs/DOC-4101

When you forgot the password and you can't use OS X, you have to use the new Recovery.

1. To boot in Recovery system, press Command and R keys in boot and hold the keys until you see the Apple icon.
2. When it starts, select Utilities > Terminal, and type: resetpassword

Reset Password

Follow the instructions in the beige and green boxes.

http://pondini.org/OSX/Password.html

Note

You should now be able to log in with the new password, but you won't be able to unlock the Keychain. If you've forgotten the Keychain password (which is ordinarily the same as your login password), there's no way to recover it. You’ll need to reset your keychain in the preferences of the Keychain Access application.

http://support.apple.com/kb/TS1544