Installing a new Motherboard with WinXP

I have a system that is running WinXP (Home) and would like to upgrade to a faster motherboard and larger hard drive. How can this be accomplished considering the dumbass protection WinXP now has? The computer store tells me that they’ll have to load WinXP from scratch. Then I’ll have to convince Microshaft that I need a new activation code. Can’t they simply copy my old hard drive over to the new one… then install my new motherboard? Win98 worked like that…. Damn, I am so sorry I upgraded to WinXP! Any help would be appreciated.