Playing media file in MediaPlayer not as Smooth as Expected

playing the same video on Win7-32, Win7-64, and Mac.All three systems have 1 GB Network connections.All were playing the exact same video. The video is scenic nature, with slow panning. It is the scenes with the slow panning that really shows the play problems.The Mac seems to play the files almost flawlessly. The pans are smooth.Both Win7-32 and especially Win7-64, the playback is jittery. The pans are not smooth, but noticeably jumpy.So, I tried making the file local to the machine, and imported and played it again. Still the playback was jittery.But windows-mediaplayer playes the files perfectly.