Zoo Tycoon 2 Problem

[Chub Chub]

Just loaded Zoo, it works fine for about 30min and then the Lap top just freezes. The only way it can be reset is by pulling the power cord and removing the battery. My laptop meets the game requirements on ram and exceeds the other requirements. I have increased the virtual ram to max setting and the HD has 11GB free. I have also loaded the latest direct X 9 driver. Does any one have any ideas. My ten year old daughter is pretty annoyed because she used her own money to buy it.