CPU Fan Size

I need to replace the cpu fan / heatsink on my p4 550 (LGA 775) and do not know how to determine the size I will need... should pretty much any LGA775 compatible (sp? sure am missing Firefox spellcheck while on wife's laptop!) one work? Any assist would be wonderful!

EDIT:

This is a P4 550 Prescott CPU mounted to an ASUS P5AD2-E Premium motherboard.

I just noticed something while browsing NewEgg... the fan that came with the cpu has little plastic "plugs" on the bottom of each of the four mounting legs that push down into the holes in the motherboard, but a lot of the ones I am seeing for sale only have what looks like a little metal rod sticking out of each leg... then I also see that they have some sort of bracket with them... I do not know how this is all supposed to match up.

Just make sure you find one that's socket 775 compatible (most are). For the bigger heatsinks you will need to remove the motherboard from the case for installation because they come with a backplate that will help distribute the weight of the unit.

With your motherboard, since there are caps right around the socket, you might want to look at a heatsink that is raised up by heatpipes in order to avoid having the caps get in the way of the heatsink. An example of such a heatsink would be the Tuniq Tower 120. This is of course not your only option, and that particular one is HUGE, but you get the idea (hopefully).

Very much appreciated!