I have an Asus m4a785td-v evo motherboard and ami bios. I also have an amd phenom II x2 555 black editon processor. And kingston hyper x 4gb ddr3 Ram. But I can't find anywhere in the bios to over clock my memory, help?

I haven't seen this board but Asus' web page for it mentions a TurboV utility to overclock from within the operating system. The manual also doesn't indicate a BIOS option for fine clock control (has voltage though) so it is probably done with the utility.