The H264 file extension identifies video data compressed with H.264/MPEG-4 Part 10 video codec. However, H264 is not commonly used extension for H.264 video, and other extension like MKV, FLV, MP4, M4V, BSF etc. are used instead, based on the actual container.
If you transcode H264 file to WMV file format (Windows Media Video), the resulting video quality can be worse, because WMV format doesn't support some features exclusive to H.264 codec. However, you will be able to playback the video even on slower machines or with older media players.