It's a DirectX game so it is probably defaulting to 60Hz. If you have an nVidia graphics card the newer drivers include a utility to override DirectX and application control of your refresh rate and always run a certain resolution in a certain refresh rate.
If you're using another type of video card that doesn't have refresh rate controls like the nVidia cards, some of them force games to launch in whatever refresh rate you've set for that resolution/color depth, in this case if you switch your screen to 1024x768x16 bit color and set the refresh rate it should remember that setting and apply it to games.
If neither of those things work for you then there are utilities around to override the DirectX refresh rate problem, just do a search on Google and you should find a tool compatible with your video card and drivers.
~SDC~
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