web2py recognize any module you have in your local Python installation, unless you have a module with the same name under /modules folder of your application.
If you are on windows I do not recommend the use of .exe version of web2py (this version is only for studies) and it has a self contained isolated Python interpreter.
Make sure you are using source version of web2py and Python 2.5+ on your windows.
web2py should import any module from your Python path, also you can drop modules in app/modules folder ], then web2py will check there first when import something.