MSI GT 725 "Turbo" Mode

Hello everyone, about six months ago I purchased an MSI GT 725 laptop and I've been very happy with it until recently. There is a button on the laptop's touch sensor bar on labeled "Turbo" and when the laptop is plugged in and turbo mode is engaged it overclocks the P8600 processor from 2.4GHz to 2.7Ghz. A pretty hefty boost in my opinion. This sounds like it would be great for gaming and in the past it has been. However, I have recently gotten more into racing games so I purchased Need for Speed Pro Street, Undercover, and the newest in the series Shift. The first two ran fine on max settings without turbo, but when I turned turbo on it ran a smoother for a while but then after a short while the frame rate would slow down considerably, something like 10 fps for about five seconds and then it would run smooth again for about another minute and do it again.

My first thought was that it was getting too hot so I bought a laptop cooling pad and it still didn't stop doing it. Any help would be greatly appreciated, thank you.

MSI GT 725 laptop specs

Intel Core 2 Duo P8600 2.4G
4 GB RAM
ATI Mobility Radeon HD4850
320 GB HDD
Windows Vista 32-bit

Note: I have experienced these problems while playing these games at 1680X1050 at all AA and Texture filtering settings.

Well, I feel sheepish...
It was the drivers. It runs like a champ now.
Thank you very much for the help Maziar and thank you for welcoming me to the forum, I'm glad to be here.