Why does my laptop get very hot when using live Knoppix DVD?

Summary: I want to use the live knoppix DVD (KNOPPIX_V7.0.2DVD-2012-05-30-EN.iso) to do a virus check on my laptop and then to do some repartitioning. After booting the live DVD, at the moment I'm just leaving the laptop sat doing nothing, while I work on another computer. But after half an hour to an hour, the laptop gets disturbingly hot to the touch near the fan underneath (see Full Details below for exact location). It feels about 50 or 60 degrees C to the touch. My question: Is there a power-management program (or whatever) that isn't running on the DVD, but should be? What can I do to stop the laptop overheating? On this same laptop, I also have the live DVD installed on the hard drive. And when I use it from the hard drive, there is no overheating. The area near the fan is then about 25 to 30 degrees C to the touch. Full Details: The problem is repeatable - every time I use the laptop booted from the live DVD, the overheating occurs. The fan is about 2 1/2 inches in from the left edge of the laptop, roughly under number-key "3" on the keyboard (above the qwerty keys). The hot area extends from the fan to the left edge of the laptop, and down towards the front of the laptop by about 4 inches. The laptop is an Acer Aspire 5755G.