After a long, difficult search (a few months ago), I found VSDC:
I haven't actually done a lot of exploring on it yet; at the time, I was really tired and just happy I'd finally found something that didn't make my carefully-crafted original music tracks sound like clippy garbage.
Tbh, I think the interface is a bit complicated, although you can tell it has a lot of functionality. I'm sure speeding up footage is within its capabilities, and I already know you can add multiple tracks.
P.S. If you really liked Movie Maker (I do, and I still plan to use it for non-music-related things) I think you can download older versions of it for free. I'm pretty sure I have an old version of it that I found online somewhere...I don't know if it's Win7, but it's the same one I used when I was a kid.