Hey Regan. Downloaded videos are to be found in the 'Downloads' folder accessible via a File Manager app like ES the Explorer or the ASTRO File Manager. You should also be able to access the videos and pics using the Gallery app. If non of the above will work as explained, then it may be that your Download Manager app is corrupt. You can try clearing data and cache from it navigating to Setting > Apps > All > Download Manager > ... You might want to consider backing up all you can and perform a hard reset is all else be to no avail. Comment below should you have any other correspondence on this and we will gladly advise further.