

I was recommended rEFInd and it’s worked wonders. Never had another boot issue since, and I did like you: physically disconnected all drives except the one I wanted Windows on. Still messed up my boot settings.
Recommend you give it a try if you dare go again.











I always thought of the CPU as the beating heart and the MoBo as the vessel/body.
At the same time: upgrading CPU often requires a new MoBo too, so I guess they are bound together anyways.
For the original question I’d say CPU + MoBo swap is a new machine. GPU and RAM are upgrades.