According to the report, the only exception to the change is for a swap out motherboard caused by defects - we guess like leaky capacitors.
Wiki said that Microsoft is getting its OEMs to enforce the rules and that a new licence is needed because the mobo defines a PC.
The article, here, gives no official comment from Microsoft. µ
* UPDATE See this Microsoft .DOC here. Scroll down to a question asking about upgrades.
Sign up for INQbot – a weekly roundup of the best from the INQ