A lot of people run 32-bit systems today . If you're among those , and your CPU is INTEL then probably it will be "locked" unless it's an "Extreme" chip ( denoted by the letter "X" in its model number ) . When a CPU is locked , this indicates its multiplier value can not be set above a particular value.
As you may already know :CPUclock = FSB * CPUmultiplierThe FSB is the Front Side Bus clock