If it's in the correct format that will play on the Tab, you can pretty much place the video in any directory you want (as long as it the directory name does not start with a .). In fact I just created a folder in the root directory of my Tablet called "Movies", put all my converted movies in that folder, opened up Gallery and it found all them without any issue. If the video is not in a supported format that the Tab can play it, it will not know what the file is and will not show it in the Gallery.