If you're computer is freezing while running a full screen game then it is almost always the graphics driver. Look in the Event Viewer and you'll likely see errors related to the graphics driver timing out and having to be restarted.
As with all graphics driver problems you need to ensure you're using the latest version, you have configured your game for what is appropriate for your card and ensure everything is seated properly. If you continue to have issues you should report the problem on the forums for the graphics card you use (e.g. nVidia, AMD). The manufacturer is the only one that can resolve this and there are generally lots of threads related to how to "work around" this problem if the issue is common.