Yes, it is most likely that the activation process will point you towards calling MS for activation, but that does not in any event mean that you will be denied a new PID. If your system is not running well with Windows 7 or you are sure you had faulty hardware, just tell them that...they will log the info though so don't think this can be repeated.
I am not in IT and do not benefit from advising the long and costly ways...
Not a Windows 7 link but still pertinent: Replace Motherboard on a Windows XP System
- I add that you should only need to make sure you uninstall the chipset drivers
...and worst case need to call activation...MS does deny new PID's, but typically not to known home phone numbers in the USA who do not abuse it.