As the answer to your original problem, access your motherboard bios (press f2/f10 or something like that during startup at the bios screen, your motherboard manual will have the instructions), access performance settings & increase the multiplier by a few numbers above stock (+1 or +2). This is the easier way (giving slight performance gain). The tougher one (giving bigger gains) can be found in the overclocking section in the forums.
As has already been mentioned, you need to upgrade the CPU cooling if you want to avhieve a bigger number, else the heat generated could kill your cpu.