When im downloading video and i preview it, i can watch whatever Im downloading. But when it is completely finished , Im only able to watch a portion until the time bar at the bottom runs out. I know there is more to see because i saw it earlier in the preview. Sometimes, if i mess with the bar and click it back to the beginning before it totally runs out, the video will continue until i have to repeat the process 6 or 7 times to enjoy the entire film. Whats going on?

That sounds like what QuickPlayer does sometimes. This has been discussed on the forum in years past but I can't recall the reason. I would however, recommend trying out a program called VLC - (click on link) _ (choose nearest mirror site) as it has in-built codecs & is usually quite reliable. And also 'usually' stops that type of thing happening.