Upgrading your motherboard voids Microsoft’s OEM agreement and a new license must be bought. Microsoft justify this amendment by stating that a new computer is built when changing the motherboard, to which the original OEM license will no longer apply.
The main point of OEM license is that, in case of purchasing a new computer, it is possible to purchase certain software for a discounted price. The terms and conditions of purchase and use are governed by the corresponding agreement. Such software may differ from the box version in product support as well.
Over time, Microsoft have changed their OEM agreement several times. Presently, the OEM license is bound to the motherboard. According to the current interpretation, a new computer is built when changing the motherboard for development purposes, so a new OEM license is required.
In case a motherboard is changed due to malfunctioning, a new license is not necessarily required but the malfunction must be verified upon request.