sorry, but no. there were two types of interfaces used by the P3, and 2 types used by the P4, but none of them are alike. the older P3's were a slot type interface where the processor was mounted in it's own housing with everything (including the fan) integrated, and plugged into your motherboard like a video card (oversimplification). the newer P3's (socket 370) and both styles of P4 (socket 429, and 478) were socket (duh) type. but the 3 processors are different and will not work in the others place. that is really not true, because the P4's did have an adaptor that would let the 478's work on an older socket 429 motherboard. but the bottom line is you will need a P3 processor. but this is where you need a second look, because the lowest speed i would buy is a flat 1 ghz. but at this speed, a P3 still hovers over $90, whereas you can find a cheap P4 and motherboard combo for not much more. I like the
pricewatch website to check on prices, but there are several others, so shop around before you make a decision.