Grrr.

Please help a newbie out... I've had this problem a lot lately. Half the time when I download a big hour long episode of one show or another I go to play it and I only get two or three minutes of playtime, like that was all there is... but the file is 70 MB! If I stop playback and then click somewhere in the seek bar, I get a new scene that I never saw in 'play' mode. It's like the video is stacked up on itself and I can only get the bottom layer when playing it. I have installed every codec I can get my hands on. I can not get 'summary' stats to show up, so I am not sure what type of MPEG it is. I don't know if it is important but I have WinXP and I have tried playing it in the newest ver of Win Media Player. Thanks for any advice!!