Could you please clarify how exactly do you plan to insert the windows media content? Using the Media Manager dialog? In addition, which version of RadEditor for MOSS are you using? Note that, in the new ASP.NET AJAX version of RadEditor for MOSS (5.x) it is possible to modify the content to be inserted into RadEditor using the editor's OnClientPasteHtml event. For more information on how to achieve the desired behavior please review the following articles:
I hope this helps.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.