Help Needed With Video Playback

Hey, I’ve been having this really annoying problem with some video files. It’s hard to describe but basically, it’s like Windows Media Player doesn’t realise the full length of the video. When it plays, just say the video is 4 minutes long, the timer only shows about 50 seconds and when the playhead reaches the end, the video just pauses but I can still hear the rest of the missing audio!

If I click somewhere near the middle of the progress bar, I can actually skip to that part of missing movie but I can only view a couple of seconds of it!

Has anyone else had this kind of problem? It’s mostly music videos that this is happening with.