If You want to Play FLV Video files (downloaded from YouTube) with any Video Player,  try FFDshow Video Decoder : ffdshow_rev1928_20080410_xxl.exe (Nightly builds by xxl) -> [Download] ffdshow_rev1945_20080417_clsid.exe (Nightly builds by clsid) -> [Download] (Right click on a FLV video file, and chose ...