I second Fraps.
A few things to note are that it is somewhat resource intensive. I experience about 2-5% drop in frame-rate when running it, but generally that's not an issue. Additionally, because it doesn't compress the video/audio, your final files end up being massive (in the order of around 4 gigabytes for ~5 minutes), so make sure you have space.
A major factor with the recording aspect is that every few minutes, when the recorded video has reached a filesize of just under 4 gigabytes (is this fixed? Someone let me know if it is possible to adjust), the entire game will freeze up momentarily for around 3 seconds as it creates a new file for the next segment of video.
You will also need to stitch them all together at the end of it. If you have Windows, I'd recommend just using Windows Movie Maker if you don't need anything fancy. Saving it in a new, compressed format will also lower the filesize dramatically (say from 100 gigabytes to 700 megabytes)