Inmagic WebPublisher PRO depends on classic ASP for its out-of-the-box web data entry. Vista does not, by default, enable ASP. You must enable it through the Control Panel:
Control Panel > Programs and Features > Turn Windows Features on or off > Internet Information Services > World Wide Web Services > ASP - Check!
Once you've done this, the IIS Manager will add ASP as an allowed ISAPI and CGI Restriction at the machine level, and add a new feature called ASP at the machine level.
Of course, this does not absolve you of the necessity to set up the right permissions for WebPublisher to update the textbase via the web, but at least you can follow WebPublisher's setup instructions knowing your IIS 7 webserver is ready to handle ASP.