Fraps 資料夾裡面的 Readme 有提到這個問題，
我把文章內容節錄出來好了。

When I replay the movie, it runs at double speed. How can I fix this?
This occurs because Fraps is not able to capture at the speed you
indicated and there is no support for frameskipping in the codec. You
can try dropping the target framerate in the Fraps dialog to 15fps before
starting the movie capture. You can also try running the game in 16-bit
color mode.