AVI to WMV 7 conversion help

I have some AVI files that are 720x480 at 29.97 fps that I need to convert to WMV at the same resolution/fps. I need to convert it to WMV 7.0 format (WMV 8 and 9 won't work for what I'm using it for). I'm looking for someone to help me convert these files over or let me know what tool you would use to do such a conversion. I tried using ff mpeg to do it, but it produces output with big blocks regardless of the bitrate used. Thanks ## Deliverables n/a ## Platform Windows Media Video 7