Hi Pityus,
it is definitely NOT possible to extract any Expansion content (e.g. Styles) from protected Pack files (.cpf) or protected Pack Install files (.cpi).
The only way for .cpf files is to import them into the YEM (only possible if the .cpf was originally made for the instrument used) and installing the Pack on the instrument as usual. Then you can save (not copy!) the desired Styles (one by one) to another location outside the Expansion folder or onto a USB stick. (On Genos or Tyros5 you can access the Expansion folder from the computer using the USB Storage Mode, and you can COPY the Expansion Styles to another location. But this is not possible on PSR-S or SX models.)
If you only have a .cpi file (which was originally made for your instrument!), you can install it directly on your keyboard. But note that all previous Expansion content will be deleted from the keyboard then.
The only way to "extract" Sounds (Voices) from (unprotected) Packs (.ppf) is to import the Pack into YEM as usual, and then use the function "Export selected Content as Pack" (.ppf again). (Unfortunately, no other export format is possible.)
By the way: With some .ppf Packs you can import the internal Samples (stored in the folder "Packs" inside the YEM User folder "C:\Users\<username>\AppData\Local\Yamaha\Expansion Manager") as "RAW" data into a Wave Editor program (and save the Samples e.g. in .wav or .aif format then). Note: This will not work with Yamaha .ppf Packs (but only with third-party Packs).