help! video sync/ file time problem?

[loudanimalattack]

After I record a video and play the file, the video seems fine, except the video time isn't right or somethiing. For instance, when I play the video, my Windows media player says the file is 6:30 minutes long, but it's actually 7:00, and the video keeps playing but the media player time stops at 6:30, as the video keeps playing.
I hope I explained this so that it makes sense. The problem with this is that when I try to upload the video, it uploads it as a 6:30 minute video, so it gets all messed up. This is happening on every video that I record.
In case I didn't describe the problem effectively, let me rephrase my problem. I recorded a video that was 7:00 minutes long. The video file plays fine and the audio seems fine and on target with the video (sync). However, Windows Media player says the video is 6:30 minutes long. The video still plays for the full 7:00 minutes, but the scroll bar, or whatever its called reaches the end at 6:30, and the video time stops at 6:30, but the video continues to play fine.
This problem doesn't effect me too much if I just want to watch the video on the media player, but it does cause me trouble because I need to upload some of these videos to a website. So to continue my example, the video I described is uploaded on a website, such as youtube, as a 6:30 minute video. It seems like the video file settings or whatever seem to say its a 6:30 minute video I guess? Is there a way to simply change this? Or is this a problem with the product?
Please help!!!!