In 4.0, although you are allowed to set audio level inside the Media Player Object Properties window by right-clicking the movie object and selecting > options..., the change has little effect on the playback of the movie. In fact, moving the volume all the way up results in playback volume of actually less than 50%.
Then, when the project is closed and reopened, the volume is set back at the default 50%.
Then, when the project is closed and reopened, the volume is set back at the default 50%.