Video Downloading

Hello, i have problem downloading some videos form the internet with my browsers, Mozilla and Internet Explorer 9. The video is 66 mins long and when i click download, the video starts to download. It tells me the size and how long the video is going to take to download for Example: "721 mo 2 h 23 min remaining" and maybe 10 mins later the download is done and when i open the video its only 1:28 mins long
does any one have a solution for this please?

Thanks in advance.