Boot up your pc.
Press DEL (its on your numpad)
Scroll through the bios till you find the cpu speed, 1936 or something like it, depending on your processor,
Change the option to manual
Now change your multiplier to 12.5
and change your memory frequency to 333
Note that you must have 333+ mhz of memory frequency
if it goes up 400 set it locked on 400-440 (what ur mainboard allows)
save and reboot
when into windows right click on My Computer and press properties, a bit in the bottom right corner it shows ur CPU Speed, if u did it right it gone up by 0,400 mhz depending on your frequency,
dont set the multiplier higher than 13.0 or ur memory/mainboard/processor/harddrive will burn out

Happy overclocking