XPS | M1530 random shutdown issue (overheating?)

hello,

Ive had my XPS m1530 for almost 2 years now.  whenever i play graphically intensive games, the game runs great! but sometimes, randomly, the machine will completely power off. I have a feeling the GPU (NVIDIA GeForce 8600 GT)  might be overheating.  I have it sitting on a flat wooden surface, with nothing blocking the vents/fans.  any ideas on how to fix the issue?