OS X Mountain Lion: Turn off FileVault disk encryption
When you turn off FileVault, encryption is turned off and the contents of your disk are decrypted. The decrypting of your disk could take a while, depending on how much information you have stored. However you can still use your computer to do other tasks while the decryption is occurring.
- Choose Apple menu > System Preferences, click Security & Privacy, and then click FileVault.
- Click the lock to unlock the preferences pane, and then enter an administrator name and password.
- Click Turn Off FileVault.
- Click Turn Off Encryption.