I made my own DLL and I searched the default browser in HKEY_CLASSES_ROOT - htmlfile\\DefaultIcon. Then use exec(path_of_default_browser_exe, "www.my_homepage.com") or execute (with the whole exe file path and homepage adress in one string).

On my PC it runs without problems, but I think it's not the absolute correct path you have to search! So if there's anybody who can give the correct way, will get a big kiss (not from me, but from anybody of your wish, hehehehe)!