Installing Ubuntu on a ThinkPad T23
The chips in T23s have the ability to run at speeds slower than their maximum, in order to save power. To see your current speed level, activate the CPU Frequency Scaling Monitor Applet. Right click on the toolbar and select "add to panel". You can search for "Frequency" to find it.
You can also enable this applet to allow you manually change the speed and scaling policy. To do that, run this in a terminal: "sudo dpkg-reconfigure gnome-applets".
These instructions are also available illustrated with screenshots.
Some technical details are explained on the SpeedStep page.