you could start by going into your bios, "soyo combo feature" menu, and upping your "cpu frequency mode" to, say, 150mhz and change your "cpu to pci divider" to 5. save this and try it for a while and see if it's stable and watch your temps.
if after some testing/game-playing all is good, then go back and add some "frequency 1mhz stepping" to bring it to like, 158mhz. try that for a while. basically, just see how high you and your computer feel comfortable with.