Arduino frequency counter

Hello,

I was trying to use the FreqCount library (I am making something that can 'measure' the frequency on an analog input). But when I compiled it this error came on my screen: C:\Users\user\Documents\Arduino\libraries\FreqCount/util/timers.h:4: fatal error: avr/io.h: No such file or directory
compilation terminated.

Is there some of you that knows how to fix this problem?

Thank you so much!

RobinC,
Belgium