The OP is talking about KOMPLETE 5 while everyone else is discussing KONTAKT 5.
Just thought I'd mention it as the pianos available in each would be vastly different.

Thanks, Mudjel. Yes, I'm kinda lost now but figured I'd just try to install the Akoustic Piano and see what happens. I don't have the Kontakt player installed in Sonar X3e and I don't want it as I never like it.

I attempted to be careful in how I stated my earlier post - there was definite attempt to discuss both Akoustik Piano, from Komplete 5, and Kontakt 5, as what I posted involves using Akoustik Piano within Kontakt 5, if it is available to the OP.
 
I USE the Akoustik Piano libraries, from Komplete 5, IN Kontakt 5, and I wrote it that way in my other post because it directly relates to a potential way for the OP to be able to access the Komplete 5 Akoustik Piano library sounds in X3, by attaching them to Kontakt 5.
 
To do the above, you would need to have Kontakt 5, most likely the full version, rather than the free player.
 
Akoustik Piano was dropped, beginning with Komplete 6, and piano sounds were expanded a bit within the Kontakt 5 Factory Library sounds.  For a time, I attempted to continue to use Akoustik Piano, but at some point long ago it quite working in either Sonar or even in Windows - think it was when I moved to Windows 7 x64.
 
SOOO, if the OP has or gets Kontakt 5, for SURE you can add the Komplete 5 Akoustik Piano libraries to Kontakt 5, and then access the full compliment of piano sounds from it - and there are some absolutely FABULOUS sounds from Akoustik Piano that I much prefer over what is available in the watered down ones that come with Komplete 6 and beyond, in Kontakt 5 alone.  I use Akoustik Piano library sounds as my go to piano sounds, all the time.
 
I do know that Kontakt reads a whole bunch of different kinds of file formats, and it certainly has no problems with the Akoustik Piano sounds.  I do not know what sound file formats something like Dim Pro reads, and I am also not completely sure if the free Kontakt Player could use the Akoustik Piano sounds or not.  Perhaps someone else can offer info on that.
 
Please note that any caps above is only for emphasis, and not any indication whatsoever of anger or tone or any of that.  :)
 
Hope the above clarifies my earlier posts that discussed Kontakt 5.
 
Bob Bone
 

Thanks Bob Bone. I'll study your posts :)

Ni instruments will only work in kontakt (or player) unless you use some translation tool (all of which are hit'n'miss) or spend weeks reprogramming the instrument in a new player, certainly aria player won't be able to use them, the only sample player that can read NKIs natively is (was) the samplelord vst, but that's had no dev for 2 years or so now...
tl/dr: use the kontakt interface or find a different piano :-)
hth

lawp
Ni instruments will only work in kontakt (or player) unless you use some translation tool (all of which are hit'n'miss) 

Agreed 100% about translation tools. There are too many nuances in sampler parameters for one-size-fits-all solutions.