Seamless looping is accomplished with the proper video player, really nothing to do with the editing. I have HD HDMI Solid State Media Players specifically for this. PM me if interested.
I guess everyone has a different opinion of "seamless" looping. Real seamless looping will not have any fade, black screen, or pause between loops. If a player has true seamless looping capability, you won't be able to tell when the file ends and restarts.Windows movie maker works great you can fade in and out between scene's to look seamless you can do it frame by frame so you add or subtract as many frames as you want and add or change music tracks . Load to DVD , Flash Drive , SD card what ever you want .
It does depend on the video itself not having any fade or black screen at the beginning or end, BUT, if the DVD player or media player doesn't have the capability to loop the file without a pause or momentary black screen, the looping won't be seamless. Windows media player may work but not everyone is using a PC to play video files.I think it depends on how the video starts and ends.
I'm using Windows Media Player on repeat too and the zombies video that I downloaded from AtmosfearFX never fades.
It's just them walking up and walking away repeatedly with no interruption in light.