Rowan, you are playing other games without problems now or some time ago? If it is not just now it could be dust in the main fan, have you tried using the dust blowing compressed air on it? If my memory is right this game has a copy protection that can create problems, one of this games ruined my dvd player, it was heating it badly and after that didn't want to work anymore and had to change it. The PC was a very good games PC and fast enough to run any game without problems.
If real is what you can feel, smell, taste and see, then 'real' is simply electrical signals interpreted by your brain
From The Matrix