Overclocking laptops is generally a very bad idea...
When it comes to OC (overclocking) the cooling is one of the most important (if not the most important) factor...
Without proper extra cooling of the CPU/Chipset you can fry the CPU/Chips quite quickly, and that's probably the case with the laptop you mention since adding extra cooling to a laptop isn't very easy..
The cooling that comes with most CPUs, prebuilt PCs and laptops are ment to handle default CPU/GPU speeds, so if you plan to overclock you will in most cases (depending on how much you OC) need to add new or extra CPU/GPU/Chipset/Case coolers to cope with the extra heat produced.
I've added this one to my CPU as well as a couple of new case fans since I've overclocked my E6600 CPU from 2,4Ghz to 3Ghz
Zalman CNPS9700 NT CPU Cooler Review
There are a few notebook/laptop coolers out there, including this one from Zalman:
http://www.zalman.co.kr/eng/product/...x=224&code=030
But as I said, overclocking laptops and notebooks are generally not a good idea because the space inside them are quite limited and so are the possibilities for heat to escape from the cases...