Be wary of the "traditional" clean installs of Windows 10 (the don't keep anything option) as there have been
numerous activation issues across all platforms, virtual and real, as what happens is that a generic license
key is generated. This causes issues with importing virtual machines among other issues with real hardware.
At the current time, the safest approach to a clean install is to do a fresh install of Win7, activate it, then perform
the upgrade.
I had just seen something recently, not sure if it was truth or not, but an article was claiming that Microsloth
has fixed issues with true clean installs by allowing older OS license keys to be used. Take this with a grain
of salt as I could not remember nor find that article.
FWIW, I did a fresh Win7 install, activated it, applied the Service Pack, and then waited until the myriad of updates
were applied to get to a point were the Windows10 installer would work. It all did go smooth. However, need to remember
to both uninstall Fusion Tools and change virtual machine OS type in preferences.