Most laptop cpus dynamically change their clock speed depending on what you are doing and if you are plugged in or not. For example if you are just browsing the web the chip may be running on half speed, but if you are playing doom 3 then it will be running at full speed. The intel vesion of this is called "speed step". You can typically change these settings in the control panel power manageent to force it to run a more reduced speeds. Also i think HT increases cpu temps so you might want to disable that. HT does not always increase speed so you probably wont notice the difference.
http://www.bay-wolf.com/speedstep.htm has some good information. SpeedswitchXP appears to be a manual way of changing the frequency of your cpu via Speed step which might be what you catually want to do.