So you have the expansion board and ddr2 on that? And you cant overvolt probably cause the processor wont let you. (perhaps with that mobo) Overvlolting is a must to really get stabile OC.

So I would suggest (if you have the money of corse) to upgrade that mother board to a DFI or even ASUS. I have ASUS and I havent found a processor I can not over volt. Of corse it is 939 and so was my AsRock dual sata. (wich I still have too.)

If you still can not over volt then upgrade the processor. Most overclockers wont go with the AsRock. They overclock but not as nicely as alot of other boards. Good Luck.