Is there not a WM Video 7 and 8 (WMV1 WMV2) MFT decoder? There is one for "Windows Media MPEG4 V1/V2 Decoder", whatever that may mean, and a different one for "Windows Media MPEG-4 V3". These are probably different, but not very common formats in the wild.
There is a "Windows Media Video 7/8 Encoder", but no corresponding decoder as far as I can find.