I'm curious as to why the output format has to be wmv? It's a fairly hideous format in that it doen't compress nearly as well as any modern codec, and editing of such files is a pain in the ass as non-MS apps can't legally edit the files without obtaining premission (which, afaik, they don't give), and MS don't make a useful app for editing the files.
I'd have thought just about any software video player will support jsut about any codec, and even hardware players support most MPEG4 Part 2 codecs (e.g. divx, xvid), so reasons for preferring wmv must be quite particular.