I make many movies with US2. Check out my video "US2 Stellar Formation" from Xolvir. Its about the first movie I ever made. You can also see the Asteroid redirect mission movie I made featuring US2.
Good movie making/recording software can be extremely expensive. Windows comes with Windows Movie Maker, which is extremely easy to use, although extremely limiting. For now I stick with Videopad. More importantly is the actual program that records the footage from your screen. I have a recorder called Bandicam. It is a very good program I must say. I have made all my youtube videos using it. Bandicam is totally free, however the free version only lets you record footage of up to five minutes. However you can take several vids and join them together into a longer one. The registered full version cost me about $50.
Other than that, its not a bad idea. Spacengine and many other programs already have a integrated screen recorder.