Starting with Windows 2003 Server, Microsoft security requires that all file types the server is going to host be registered with the server via MIME types. If you have recently migrated from an earlier server to a 2003 platform, you may notice your tours do not work until these MIME types are added to the server's configuration.
The MIME type info is as follows:
file extension=.ips application/x-ipscript
file extension=.ipx application/x-ipix