FlashBack Player is designed specifically for FlashBack movies so will not play any formats except for .fbr files.

 

So you cannot play .mp4, .avi, .wmv or any other video formats in the Player.

 

However, you can use the 'Convert Video File to FlashBack Movie' option in the Player's Tool menu to convert .mp4, .avi. .wmv and .flv files into an .fbr file, which can then be opened by FlashBack.