A LOT of the ability to overclock is based upon what motherboard you have - if you have a straight out-of-the-box DELL or similar, your overclocking ability is severely limited. However, if you have a "high performance" board like an Abit, Tyan, or Asus you have infinitely more possibilities. Celeron's used to have the clock speed ingrained into their chip architecture, which made for interesting results when overclocking. There are ways around it, but again, it requires a performance board. And overclocking may not give you much more juice out of a celeron as you won't be increasing the cache. You may be able to boost the FSB speed up to that of the equivalent P4, but again, this is sketchy and not recommended unless you are willing to take the chance of frying out your entire system