That's not strictly correct. XP Pro OEM is quite generous when it comes to re-activations. Changing single components at once, e.g. gfx cards, memory and so on shouldn't trigger re-activation.
Changing your motherboard will almost certainly ask you to reactivate, but if the rest of your components haven't changed, e.g. HD, CPU, memory, then activation should be fine.
In any case, if you're regularly formating and/or rebuilding your system due to upgrades then you should be taking steps such that you don't to keep re-activate after every clean build, such as:
a) taking an image of your HD after a clean build
b) doing a back-up including system-state using the back-up tool in XP Pro
c) backing up your activation database files
d) all of the above
Assuming you're not a rampant pirate, you can speak to the nice lady at Microsoft and she'll give you a manual code to enter to re-activate. But as I've said, reactivation should be a rare event indeed.
For instance; I have an OEM copy of XP Pro and my hard drive recently died; I had a full back up of the OS (including system state) so I just put a clean copy of XP pro on the new hard disk and restored by previous back-up straight over the top. Result? Everything back to just before the HD failure and no need to re-activate.
Here's some handy links:
http://www.microsoft.com/technet/prodtechnol/winxppro/evaluate/xpactiv.mspx
http://www.theeldergeek.com/activation_workaround.htm
--
Richard.
