P-51D 44-11661 QP-X "Mustang Sally" updated for use with DCS 2.1 Normandy.
( Official reg: 44-74494 )
Unrar, copy and paste the containing folders to ( C:\Saved Games\DCS.openalpha ( or DCS 2.x .... ) \Liveries\P-51D ) if you have already created such a Liveries folder.
Otherwise I strongly suggest to create a Liveries folder for all your downloaded skins/skinpacks in the Saved Games section.
This way, you keep your DCS install clean.