Best to do a search on google and see if anyone else has tried it on your make and model of laptop. My little netbook is quite happily overclocked by a bit and it could go further if I felt like pushing it but I always remember the weather.
You have to remember that ambient temperature and humidity changes year round and unless you're doing it on the hottest day of the year it's a bit of a risk to push it because it might be fine most the year but all it will take is one exceptionally hot day and you risk irreversible damage. Also bear in mind that it's not easy for heat to escape a laptop and most onboard graphics chips only have a passive coolant device (such as a heatsink). Also if your fans get clogged, further restricting airflow this can kill it very quickly.
I doubt you'll see much of a performance increase anyhow to be honest. You're better off trying something software wise to squeeze a little extra out of it. If you want a performance boost, set the Nvidia control panel settings to Maximum Performance and get used to lowering and disabling things that have minimal graphical effect in your games but can be resource heavy (like high quality shadows.) Or do a few balancing tricks such as lowering the in-game resolution and upping the anti aliasing or vice versa. You'll also find your card does some things better than others.
Finally you can try using Game Booster which I use from time to time on my netbook and I squeeze an extra 3-8fps on average from my games using it. http://www.iobit.com/gamebooster.html