The upgrade is going to happen regardless and I guess it will be a suck it
and see situation as to what I have to do with mywin7 installation
afterwards.
I have not contributed anything to your inquiry, but would really appreciate
if you could share with us by letting us know the result.
Also, you mentioned that you will replace a new motherboard, CPU, and RAM.
I don't know if it's possible for you to replace one component at a time
(e.g. a new motherboard with the old CPU and RAM, provided they are
compatible with the board) instead of replacing all three critical
components at once.
The reason is that sometimes the activation scheme and Windows operation are
based on the accumulated scores/points of critical components changed.
Replacing one critical component at a time is more like a system
upgrade/repair while replacing all three critical components is more like
moving to a new system.
So by replacing one at a time, you might avoid a reinstallation or
reactivation.
In any case, just a thought and good luck!!