Not sure if you've got it working yet, but it at least looks like you're getting closer.
1) I see you found the sound sets located in
C:\ProgramData\Avid\Sibelius 7\Sounds. You can put
VDL_SoundSet_7.0a.xml there with the other default sound sets if you really want to, but I recommend you instead place it in the Sibelius User's folder (
Installing A Sound Set). Definitely do NOT place them in both places.
2) 32 vs 64 bit:
C:\Programs Files points to 64 bit applications and
C:\Program Files (x86) points to 32 bit applications. Assuming you're wanting to run Sibelius in 64 bit, you can ignore the x86 directory. So, place just the
Kontakt 5.dll file (make sure it's 64 bit) into
C:\Program Files\Avid\VSTPlugins. (I highly recommend you do not place either of the two DLL files that has "out" at the end of their names - they're unnecessary and just clutter the Configuration dialog.)
Let me know how you get on.