My mobo just crapped out on me so, I have to buy a new one. Am I correct in assuming that the Windows 10 pro activation key that I used with the old mobo will not work with the new mobo?
So, if the old mobo was an AsRock H310 and I buy an ASUS H310 mobo I should be okay?Get same model motherboard for replacement (at minimum it has to be same chipset motherboard). Then you might be able skip re-installation of windows.
It still may require re-installation for some of drivers - chipset, graphics,lan,audio.
Use instructions listed here, how to reactivate windows after hardware change.