1) Checks if the root folder is protected and aborts if it is (we can't scan folders if the root folder is protected)
2) Checks if WebDAV is enabled on the server and aborts if it isn't. The check works on IIS 5, 5.1, and 6.0 (hasn't been tested on others)
3) Added support for finding the vulnerability on IIS 5.1 (Windows XP) -- 5.0 doesn't appear to be vulnerable in our tests