The clock speed of your processor is computed from the front side bus x multiplier.
For that specific CPU, I beleive the multiplier is 12.5 and the front side bus is 166MHz. Thus your CPU frequency is:
12.5 x 166 = 2083MHz.
To overclock your CPU you need to increase one or both of these. For example, in your computers bios, I would suggest lowering the multiplier to about 10x and then increasing the FSB by 1 or 2MHz at a time as far as it will go while still being stable, then increase the multiplier 0.5x at a time, till it has gone as far as it will go while remaining stable. To improve stability sometimes increasing the core temperature helps, but this also produces more heat.
Do you know what your CPU and case temperatures are just now?
Also, check out the stickies in this forum for loads of useful tips.