Let's go over 2 cases where it will do that and it's normal. One case is the old software conflict issue and the other is the old laptop.
1. Software conflict. If you read http://forums.cnet.com/7723-6122_102-510824.html we found one of the common software conflicts that made the machine feel slow and work hard. Such a system would be a heater.
2. Old laptop with say the Nvidia 8400/8600. These are now failing and you'll see one sign where the heat production goes up. It's the first stage of the failure and later it will stop.
I see you only wanted to discuss this without looking at your machine as there are so little details to work with.
I know that laptops can overheat but this is a specific case..
Lets rewind the clocks back 3 months ago my laptop normally runs at 40-45 C but due to some unknown reason it suddenly starts to show high temperatures up to 60-70 even at standby.. So i Re install my OS and everything was back to normal again but 2 weeks ago this problem has started again and this heating is definitely slowing down all my games and apps.. What could be the reason..? is there a solution for this other than re installing the OS..?