Help! unable to locate 'p18cxxx.h'

Recently I downloaded Kevin Watson’s Gyro code, without changing any thing on it (mplab 7.20 running on windows xp) when I tried to compile it I got an error of unable to locate ‘p18cxxx.h’. However in other projects using the default code (from ifi) I looked and found the #include <pc18cxxx.h> and then compiled them successfully (I also wrote some code for driving which also worked). I have tried downloading another version of the gyro code from without any change in the error. Any Ideas?

In the project build properties, make sure all the paths are correct.