Turn off encryption on filevault2 second HDD I have an Early 2011 MBP on which I installed an SSD (in the SuperDrive's bay).
After that I enabled FileVault2 encryption on both the SSD (which has the ML 1.8.2 install) and on the original HDD that's currently mounted at boot-time on /Users (so all the storage for the users go on it and it's still encrypted no matter what).

I would like to add a second (and maybe a third?) partition to the HDD so that I can experiment with Windows 8 (and maybe the latest Ubuntu?) but the error I receive is  

Error: -69741: The target disk isn't eligible for reversion because it wasn't created by conversion or it is not part of a simple setup of exactly one logical and one physical volume

Is there anything to do ?
What methods have you used when trying to disabling the encryption on your encrypted non-boot drive? Here's some ways I know about:

Using Disk Utility


Boot your Mac and hold down ⌘-R (Command –R) to boot from the Mac’s Recovery HD partition.
Open Disk Utility.
Select your locked hard drive.
Under the File menu, select Turn Off Encryption…
When prompted for a password, you can enter your password for the drive. Once provided, decryption of the encrypted volume should begin.


The drive should begin decrypting.

From the command line


Boot your Mac and hold down ⌘-R (Command –R) to boot from the Mac’s Recovery HD partition.
Open Terminal.
Run the following command to get the UUID of the encrypted drive: diskutil corestorage list
Once you have the UUID, you can unlock the drive using the following command: diskutil corestorage revert UUID -stdinpassphrase
You’ll be prompted for the password/passphrase of an account that’s authorized to unlock the encryption. Once provided, decryption of the encrypted volume should begin.


The drive should begin decrypting.

For more information, see here:

Unlock or decrypt your FileVault 2-encrypted boot drive from the command line

Using Disk Utility to unlock or decrypt your FileVault 2-encrypted boot drive