If you find ffdshow only in BSPlayer's folder, then it's not system installed but only local. Run codecmanager.exe from BSPlayer's install folder and uninstall ffdshow. Then install ffdshow for system, using
Free-Codecs.com : Download FFDShow MPEG-4 Video Decoder 2011-11-20, FFDShow MPEG-4 Video Decoder 2011-10-13 and FFDShow MPEG-4 Video Decoder 2011-11-20 x64 : FFDSHOW is a DirectShow decoding filter
If you have Vista on 64 bits, download x64 version.