There's a lot of frustration over the compatibility of small popular video cameras and some basic editing software packages, as far as I can see. For example the popular Flip cameras produce excellent results but MP4 is not a great editing format and may not even be viewable on some laptops running Microsoft Movie Maker.
I've been having a look at VideoPad which includes a free video editing software version for Windows. I have not tried it in earnest yet but it looks quite neat and can handle a number of file types – probably more flexible than Moviemaker in this respect. It might be a good companion for the Flip cameras, but let's see.
A big weakness with many free video editing packages is the limited number of audio tracks. Generally you can cut the audio with the pictures and add a commentary layer but that's about it. The number of audio tracks is a difference between amateur and professional editing packages. Great audio can have a huge impact for your video.
A lot of fun can be had preparing an exciting audio track so think about using another free programme Audacity to create muti-track audio for your video. You can usually open the video file directly in Audacity, edit the audio and then re-import the finished audio back into the video editing software.
VLC Media Player
Finally, if you have difficulty viewing some video files you might have a look at the free VLC Media Player. It plays many file types and can do some media conversion as well.