Editing audio in Windows Movie Maker Live?

I inserted a video, and the audio is terribly out of sync. I need to sync up the audio, but there isn't a separate track for audio and video unless I add my own music. You can't edit the audio that is present in the original file, or so it seems. This seems wrong. How can anybody release such an inefficient product? I might be missing something, but it seems that Microsoft decided to make it as simple as possible, and ultimately got rid of a lot of essential features. ESSENTIAL. So, any suggestions? Does anybody have some free video editing software that supports mp4 files? I tried Wax, but I don't know what was going on there.