The longer you use it, the hotter it gets. Generally, any exterior piece of a notebook that gets warmer than 95 degrees Fahrenheit is just plain uncomfortable. Worse, excess heat can cause damage to your system. Passive devices, such as the Targus CoolWave can offer some relief. But for real results, you need a fan that actively blows cool air up toward the notebook to wick away hot air.

To test just how effective these devices are, we measured the temperature changes before and after using coolers with an Acer Aspire 5738PG. We tested immediately after powering on, after playing a digital copy of Smokin’ Aces for 15 minutes (with the brightness and volume set to 50 percent), and while converting a 115MB MPEG-4 file to AVI while compressing a 4.97GB folder of mixed media. We pointed our temperature gun at the center of the underside of the notebook, the touchpad, the lid, and between the G and H keys on the keyboard. Without a cooler, the 5738PG reached temperatures as high as 97 degrees. Read on to find out which model kept the system coolest.