How to Use Migration Assistant in Mountain Lion
Migration Assistant in OS X Mountain Lion is pretty much a one-trick pony, but that pony is a prize winner. You use the Migration Assistant to transfer your account and other user information from another Mac or another volume on the current Mac to this one.
You need to authenticate as an administrator to use it, but it’s a pretty handy way to transfer an account without having to re-create all the preferences and other settings.
When you first installed Mountain Lion (or when you booted your nice new Mountain Lion-based Mac for the first time), the setup utility asked you whether you wanted to transfer your information from another Mac. If you answered in the affirmative, it ran the Migration Assistant.
It’s not just for new Mountain Lions. You can launch this puppy any time to transfer all or some user accounts, applications, settings, and files from another Mac or PC to this one. Or use it after replacing a hard drive or reinstalling OS X. Last but not least, Migration Assistant can import user accounts, applications, settings, and files from Windows PCs as well as Macs.