Video overlay, picture in picture, or split screen?

Hi, I've been researching this and I'm not finding that this is a feature available in Windows Movie Maker, but can you please provide suggestions/ideas on how I can do this?

I usually use Windows Movie Maker to create my YouTube videos (cover songs, etc), and I'm wanting to do one, where I play multiple videos simultaneously, while retaining the sound in each, so that they play and the volume works on the multiple ones at once (doing an a capella type idea for a video, and need them to play simultaneously). Is this possible with a plugin or anything through Movie Maker? Or is there an alternative? Thanks!