Not 100% sure that you can use it on XP, but your best bets for free (legal) recording programs are probably going to be Open Broadcaster Software (OBS) and LoiLo Game Recorder. Both are completely free and don't have a watermark. OBS is more feature-rich, but much more difficult to learn. It is also more memory-intensive. LoiLo is pretty easy on your system, and super easy to learn as well. However, it lacks some of the features that OBS has.
Fraps is only free if you obtain it through less-than-legal methods.