If you don't sure how to get Limited Edition CD with Retention OST - here is instructions:
You must open a place, where Retention installed. Full path will look like:
(In x64 versions of Windows 7, Windows Vista, Windows XP etc)C:\Program Files (x86)\Desura\Common\Retention\Retention - Original Soundtrack\
(In x32 versions of Windows 7, Windows Vista, Windows XP etc)
C:\Program Files\Desura\Common\Retention\Retention - Original Soundtrack\
This is a place, where OST located.Also there is file "I_Want_Limited_Edition_CD_With_Retention_OST.doc" with instructions how to get Limited Edition CD with Retention OST.
Enjoy!