Moved the topic, it has nothing to do with grafic cards and hardware.
The framerate should reduce only to that value you set FRAPS to record (in the FRAPS options).
Its absolutely not normal that your framerate goes towards 0 and the game crashes... never encountered such a problem. If the hard disk is full the recording stops automatically, thats my problem recently.
A final tip: when recording, you get the best result when fps smoothing is active and set exactly to the FRAPS fps.