Installing ax12.h library

I downloaded the file that contained the BioloidController library (which had ax12.h, ax12.cpp, BioloidController.h, and BioloidController.cpp) and copied it to the Libraries file for Arduino IDE. Unfortunately when i click on the libraries tab and then Bioloid, it brings up "#include <ax12.h> #include <BioloidController.h>" but only the BioloidController.h is actually recognized (changes to orange font). ax12.h stays regular text. whats wrong?