moving a hard drive

im moving a hard drive to a new motherboard (primary master)
has the OS installed on it
simple question - do i need to wipe it clean and reinstall ?
if yes/no or even (mabey) what potential issues am i facing?

thanks

out of striaght morbid curiousity - why reinstall everything
that is, what happens if you dont anyway?

thats pretty much what i thought

though somewhere in the back of brain .... i thought .... mabey..... with all the advances in plug n pray and what not - wiping out all the hardware devices before the move would allow more generic drivers to load or some such thing and windows would just reinstall new drivers for the new system

pipe dream i know - who am i for thinking things might be just a little easier - truth be told though i dont mind it to much - all my important stuff is on another drive - just windows and my office apps are on the main drive
fresh install of windows never hurt anyone - though i'll be migrating to XP instead of using W2k this time makes me wonder how excited the verification process is going to get - im reusing a copy of XP though its not currently installed on any other system - i did activate it on this computer at one time then removed it and reinstalled 2000 - spose ill find out soon enough