You guys can try Speedfan.
You will have to try random PLL's (the crystal clock that sets the FSB mhz), and use CPU-Z to see if its working. This allowed me to overclock my 1.2ghz Thunderbird that had an Asus motherboard from an HP in it (no OC options). You wont be able to change voltages though, so you will be lucky to get any extra mhz you can get.
Other programs usually wont allow you to try random PLL's the way Speedfan does.