According to an (older) book I have, the windows SDK should have a dirrectory (\SAMPLES\DEFPROCS\) that contains source code for the default window procedures. My SDK does not. (My SDK is old, but the book is far older). If you can e-mail me the files from there (or tell me where they might have been moved to/renamed to), I'll give you an A. Two of the files are DefWnd.c and DefDlg.c. However, there might be more, I don't know.
(If you e-mail the files be sure to answer the question so other's don't sent them.)