The sims 3 has provided us a tool in the game to capture pictures, and record the video (press C to capture picture, and V to record video). But its (video) quality is very low (even when you set it to max, it still low). You can use that tool to record the vids. And when you're done, you can find your video at: \Documents\Electronic Arts\The Sims 3\Recorded Videos\
Personally, I think you should use this program for a better quality video. It's called FRAPS. It's a good tool for gaming that show us the fps (frames per second), capture pictures, and of course, record videos on high quality
when playing. You can find this program at this site:
http://www.fraps.com/download.phpGood luck, and happy simming
