Due to security issues with Windows 2003 Server, you need to implicitly include all mime types for files that you are using in your project. Typically speaking, if you are using ActiveReports 2.0 over the web and you are loading it with a report in RDF format, the RDF extension needs to be registered in IIS. You can do this with the following steps:

1. Open IIS 6.0.
2. Right-click on the server (if it is a root application) or the virtual directory (if it is in a subdirectory off of the website) and select Properties.
3. Click the HTTP Headers tab and select "File Types" under Mime Map.
4. Click "New Type", enter the extention (IE ".rdf") and a content type (IE "ActiveReports Report").