RDP does not come with a USB tunnel or bi-directional audio connecting to XP. You will need Wyse TCX Suite for the webcam and bi-directional audio. You can download a evaluation version from the download page. Just install the "server" piece on the XP your connecting to. The "client" side is already part of the WTOS code.
Hey guys! I ran into this post by accident and thought that my message would be of any use to you or someone ales. Recently I had a similar problem with my webcam. I couldn't redirect it to my remote session with Citrix. I googled and found an app USB for Remote Desktop. Check for it.