If your Celeron is of the same generation as that p3 in question then you won't have to worry about voltage. In short just drop it in and put the cooler on then you are good to go. Some boards are compatible with the older Celerons (250nm) and can still use Coppermine (180nm) pentium 3 and p3 based celeron. If your board is new enough get a Tualatin based p3 or celeron that are 1ghz+ you will see a nice boost. I still got an old compaq with a 1.4ghz p3 and it can still handle a lot of modern apps for its age.