Just as a courteous advice, I wouldn't recommend to do so. Heat is an issue in laptops, and can severly affect reliability/durability. If you want your lappy to run smoothly for quite some time, don't o/c.
The GF6600 in my m5500 goes up to 70°C in full load, it wouldn't be reasonable to overclock it, and anyway it wouldn't change much, considering that the core temp shouldn't go much higher than that.
My 2 cents worth... "Save a lappy."