In Ubuntu Hardy Heron there is a bug on the cpufre-applet, if you can’t change the frequency of your CPU try this:

  • Remove the currently installed cpufreq-applet from the main panel, right-click on the applet and then select "Remove from panel",
  • Open a new terminal window
  • Change the file mode bits for the applet typing the following comman

# sudo chmod +s /usr/bin/cpufreq-selector

[sudo] password for <user>:

  • type your password
  • close the terminal window
  • right-click on the main panel
  • select the "Add to panel…" item
  • from the dialog box that will appear select the CPU Frequency Scaling Monitor

Now you can try to change the frequency of your CPU, it should work fine.

 

GG1