Exporting to Windows Media Video requires you to set a video codec ID, audio codec ID and an audio format ID. These ID numbers are the same as those used by the Microsoft's Windows Media Format SDK classes to identify codecs and formats. You'll need to use these classes to find the ID numbers of the required codecs.
To determine supported WMV video and audio codecs, use the Windows Media Format SDK class IWMCodecInfo3. Its GetCodecInfoCount method returns the number of supported audio or video codecs.
Each WMV audio codec supports a number of formats, where a format typically has a sample rate, number of channels and either a variable or constant bitrate.
Once you've used IWMCodecInfo3::GetCodecInfoCount to discover the number of supported audio codecs, you can then use the GetCodecFormatCount method to discover the number of formats supported by a particular codec, and GetCodecFormat to return the details for a particular format.
Consult the Windows Media Format 9.5 SDK documentation on http://msdn.microsoft.com for details.
Important Note: Windows Media Player 9 or above must be installed in order to export to WMV format. PCs that do not have this pre-requisite installed will not be able to export to WMV.