Generally if you buy an OEM edition it's meant to be bundled with something like a Dell.
Now if you update the Mobo for anything other than a defect then PC is no longer either accepted by Dell Warranty nor is it a Valid OEM license since it isn't the original hardware the OEM was shipped with. This is because Windows is sold to companies at a reduced price and they dont want people just transfering Windows (Like you can do with FPP).
If you usually have the need to upgrade a mobo, you have Windows FPP and not OEM. Really, this is meant for buying these types of PCs in bulk for something like an office or a school.