I'm just curious on this since my friend has told me to never overclock my laptop even when the laptop has an overclock feature. Should you ever overclock a laptop? If you wish to get into specifics onto what kind of laptop is in question then it is a MSI GX660.
Windows 7 Home Premium 64-bit
Intel Core i5-450M 2.4GHz
ATI Mobility Radeon HD 5870 Broadway XT
Considering I've had many laptops die due to heat induced failure or degradation of performance (typically at the 4 year mark) I would say you only only speeding up the demise of your laptop. I have one laptop that is 7 years old, but is starting to exhibit heat issues. The one that is still alive wasn't built with power in mind so it doesn't put out as much heat.