Well, I’m not sure exactly what happened, but I recently worked on a Windows XP laptop that was freshly rebuilt. Classic ASP pages worked fine, as did .NET aspx pages.
However, suddenly IIS stopped being able to serve classic ASP pages (.NET still worked fine). It just returned a “500 Internal Server Error” The symptoms were exactly the same as an article on MSDN, (two events in Event Viewer, one for W3SVC and one for DCOM) but we couldn’t get the suggested fix of making the passwords the same in both the IIS metebase and Windows.
It turned out, the easiest solution was to uninstall and reinstall IIS. It takes about 20 min and you’re done. Take lunch between the two and you barely notice what’s going on.