I had to replace an AMD64 one,part of it snapped and the heatsink fell off .The user kept turning pc on,mad thing is it booted to windows before crashing.
What a nightmare replacing it was.It wasnt screwed on ended up having to dig these stupid plastic lugs off
Hope the P4 is easier just be careful
Ask around your local pc shops,If im not mistaked some chips come with a spare one of these and they may well have one lying around