Thread: Error with include files

I have some source programs. When compiled they give me the following error:

Code:

Compiling...
foo.cpp
e:\source\foo\foo.hpp(14) : fatal error C1083: Cannot open include file: 'haa.h': No such file or directory

Line 14 of the file 'foo.hpp' looks like this:

Code:

#include "haa.h"

Can anyone tell me what causes this type of error and how I can go about fixing it?