In my ASUS board, it doesn't have a setting to change the ratio. So just set the RAM frequency to the lowest possible, this will change the ratio (it will probably be 667MHZ) Don't worry that it's lower than the RAM is supposed to run at, it will be running at 800MHz once you've OC'ed. Next change the FSB to 400, and the multiplier from 9 to 8. Then save and reboot. If it won't boot into Windows. Go to your BIOS, and up the Vcore to around 1.3V. Good luck!