I have always typed in CD Key when prompted, but do not activate until after I have installed all primary hardware drivers.
In past if I activate a product right away, then install drivers for hardware after, I have WGA and subsequent activation problems.
So if I always wait to activate after installing hardware drivers, things have seemed to work better.
I turn off Automatic Updates and do those manually as well.
I can go off tests I have tried, which give results I say above, but I could try doing other ways to help confirm.