Those older processors have to be over clocked by raising the Front Side Bus (FSB). We call it the Base Clock these days (BCLK) but your BIOS may refer to it as the FSB. Note when you are FSB over clocking you will over clock your RAM and your Bridges so you will need fast RAM and you will need to monitor your RAM temps and Bridge Temps.
As to how to do it. You raise your FSB then boot into Windows and run a CPU and RAM tester like Prime95. If the system crashes you raise your Vcore and or RAM voltages to stablelize it. Be sure to not exceed the max voltages on these devices and to monitor their temps as you raise the voltage the temps will rise too.
There are some over clocking guides out there I recommend you read them. Over clocking these older systems can be dangerous unless you know what you are doing.
http://www.wikihow.com/Overclock-a-PC