Every digital camera--even the camera on your smartphone insists on storing photographs in a folder called DCIM. DCIM (for Digital Camera IMages) became the default directory structure for digital cameras. Mostly it exists to keep everything organized. When you put a memory card into a camera, the camera immediately looks for a ‘DCIM' folder. If it doesn't find such a folder, it creates one. Likewise tablets are designed to look specifically for ‘DCIM' folders on any media inserted into it. That saves time in scanning said media for images--and it prevents the software from importing images that your camera didn't capture. That is the reason why you cant play a video unless it is in the DCIM folder.
Thanks but we are not talking about a digital camera here, we are talking about a tablet PC. Why can't you change the default directory that the video player looks at for its media and what is the video folder for if not for video?