The overheating isn't causing your laptop to lag in games due to the heat itself. I have the 4 core version of your laptop, which is essentially the same, and the system is designed to "throttle", i.e. downclock the speed of the graphics card when it hits a certain temperature, in my case it is 84 degrees C. I think Dell added this as a "safety" feature, although in my opinion it's completely unnecessary and hinders gaming performance since most GPU's can handle up to 105 C before they suffer adverse effects. When the GPU throttles you will certainly notice a lag in gaming. The 4 core version got a BIOS update that removed this feature, which removed all lagging during games for me. Now I just have to use a temp. monitoring program...