A Sony laptop won't have any overclocking options unless you use a software option but that is probably not enabled in the drivers for this laptop. Riva Tuner may work, but you are putting your laptop at risk of an early death. Probably not for much more than a 5% performance gain which is not noticeable outside of a benchmark test score.
If you want faster video, you have to get a new laptop with a faster video card. Or lower settings in games. It looks like that card can run many games at low to med settings pretty well.