Originally posted by Ishan.
First click on File then Import into Collection
After the window opens , there are two text boxes 1 for file name and other for file type . Set file type to all files as shown in the img. then select the video u want. But be sure that the video format is supported by the movie maker !!! I hope this helps !!!
Try the ffmpeg if you are familar with commad lines, and you can also try the zamzar which is online converter, or try the wondershare free video converter which has pretty easy to handle interface. Hope it helps.
