well if this is your board you can only use any of the cpu listed from the mother boards cpu support list with the latest bios ,and only ddr2 is supported on it
[ The following table shows the supported CPUs for this motherboard ]
https://www.asus.com/Motherboards/M2N/HelpDesk_CPU/
this is just a guess on what board you ''MAY'' have with the limited info your able to give