You need to download GCC ( C++ compiler ) to compile the modules.
From Mark on the Beta thread :
http://prdownloads.sf.net/mingw/MinGW-3.1.0-1.exe?download
From Mark on the Beta thread :
'Build modules' requires MINGW to be installed under Win32. You will also need to add mingw/bin to your PATH env variable and add an env variable called MINGW pointing to the root mingw dir.
http://prdownloads.sf.net/mingw/MinGW-3.1.0-1.exe?download