How to compile modules

I am having trouble compiling some modules for php4 and IIS. I am attempting to build the pdf module, and I get the following error: ------------------------------ Compiling... pdf.c e:\php build\php4\ext\pdf\pdf.c(41) : fatal error C1083: Cannot open include file: 'php.h': No such file or directory Error executing cl.exe. -------------------------------------- I have followed all of the directions on the php site on how to compile for windows, and I still get this error. Can anyone give me a hint on how to get this to work. Other modules such as ftp compile correctly... Jeremy