You'll find the PrChannel presets here:
 
C:\Cakewalk Content\SONAR Platinum\ProChannel Presets
 
To load one of the presets, go to the ProChannel header, hover over the preset name, click on the Folder button, then navigate to the folder above (if needed). All the preset names start with Ac Guitar, like "Ac Guitar - J-15 Articulated."
 
For information on the presets themselves, go to page 12 in the Cambridge release eZine.
 
Let me know if you need anything else. Have fun!