A few suggestions:
Turn Turbo Off (you probably have).
Manually Increase the fan speeds.
Get an underside laptop cooler tray.
Leave it at default clocks (2.66GHz), or only overclock if the core voltage remains the same.
If need be use Power Options (Vista/W7) to reduce the voltage and clocks slightly.
A trick you could try, but not normally the thing to do, is to remove the battery and run directly from the mains. Batteries heat up and use electric - not all laptops can run straight off the mains.
Good Luck,