When you playback an inp in DOS, you don't need to put the .inp extension for the name of the inp you're trying to playback. For example if you wanted to watch a Kung Fu Master recording, you would type:(posted 9601 days ago)mame kungfum -playback kungfum
A more simple way is to use MAME32 for playback, it takes a couple of mouse clicks to play back a game, and is useful to have running in a window with speed throttling on (F10) for those longer recordings.