Processors never run at the advertised speed under normal conditions. Also the fact that you have a celeron 1.2 probably means your running the slower sdram 133 memory which will limit you. If you want to overclock it, the motherboard must have the features to allow it. If you overclock, be carefull especially with heat, and keep in mind the processor may have a shorter lifespan due to stress. Be cautioned with temperatures over 50 degrees Celcius. If you overclock do it in small increments until the system starts to become unstable, then back off. To control heat better you may need a better fan and use a high quality thermal compound on the heat sink, like Artic Silver 3.