HT1338: OS X: Updating OS X and Mac App Store appsLearn about OS X: Updating OS X and Mac App Store apps
Currently Being ModeratedOct 24, 2012 4:18 AM (in response to mks1008)
It can't be retrieved but it can be changed which is effectively the same thing except for the Keychain Access application which will retain the old password.
If you wish to change your Admin password, follow these instructions.
Currently Being ModeratedOct 30, 2012 12:23 PM (in response to mks1008)
It is useful to have 'root user' enabled for situations like this.
It is normally possible to enable the 'root user' without knowing an admin password or having an installer DVD - Google for details.