Searching for this model laptop reveals this forum thread talking about how to manage power on that laptop.
First install the utilities:
sudo apt-get install cpufrequtils
Then set a conservative governor:
sudo cpufreq-set -g conservative
According to thinkwiki:
They differs in the way they scale up and down. The ondemand governor switches to the highest frequency immediately when there is load, while the conservative governor increases frequency step by step. Likewise they behave the other way round for stepping down frequency when the CPU is idle. The conservative governor is good for battery powered environments on AMD64 (but may not work on older ThinkPads like the T21). Ondemand may not work on older laptops without Enhanced SpeedStep due to latency reasons. Anyway, for recent enough Intel CPU, ondemand is the one recommended for power efficiency (over userspace, and even over "powersave") by the Intel's kernel developer Arjan van de Ven
Though that might be a little bit out of date. You might want to try it and see how the laptop runs for a while.