For the computer gurus! Changing icons!

[Rapley]

Ok, well, i've been struggling to find something on the net to help me, so i thought i'd take a stab at it here.

I want to change the icon of a certain type all at once. So, for example, the default yellow folder icon (used for ANY folder in windows XP basically). I would like to change them ALL to one i've downloaded. Normally you can just right click, then go to "customize", then "change icon". Which is all good, if i wanna do like, a couple icons, but i wanna do all of the same type. Anybody have any clue how i can do this?

Thanks

Josh