75 C Temprature in mobile Core 2 Duo

That's too warm. The fact that it's shutting off means the built in safety measures are kicking in to prevent damage from occurring. Make sure you are using the laptop on flat surfaces and not on carpeting or bed spreads (they block the air flow). Otherwise, some options:

1) Have you ever cleaned out the air vents in the laptop? If not, go to a Staples, Best Buy or other PC store and buy a can of compressed air and blow the dust out of the vents. Dust is a killer in terms of heat.

2) Depending on the age of the laptop, the thermal paste may have dried out. You can replace it, but it requires knowledge of how to take the heatsinks out of you laptop. It will also more than likely void any sort of warranty you may have left.

3) Buy a laptop cooling pad. I would try the other options first since they cost less and would treat the problem instead of just the symptoms.