i cant help you unlock your gpu,i did have the same one but it overheated and died...
but you have other splutions available.
reformat/use your pc hd in a caddy/buy a big usb stick/put a new new hd in your lappy and hook it up to the monitor you would have had your 62/6600 into.
i undestand that your wanting to get as much mileage out of your computer that you can,
most people do the same but i think this is the most difficult way to do so?
and for what real gains,surely it will be a couple of fps max,the same as adding more RAM possibly