As you prepare to clean install Windows 10 please take the time to read my article entitled How to make sure your free copy of Windows 10 is activated which was posted after this one.
An inplace upgrade must be completed first on your Windows 7 or 8.1 system to generate the proper codes for Microsoft to validate/activate the OS on that hardware.
The article has much more detail.
One of the big questions over the last few months about the release of Windows 10 was clean installing onto a former Windows 7 or 8.1 system and retaining proper activation of the subsequent Windows 10 install.
There is more than one way to get a clean install of Windows 10 in an upgrade scenario like this.
You could create USB installation media using the media creation tool Microsoft released for Windows 10 today and then boot from that, remove partitions and then install to that cleared drive. That process asks for a product key to be entered and I was unsuccessful in entering a Windows 7 or 8. key for that. The product key step can be skipped so I did that and removed all partitions on the SSD and did a bare metal install signing in with my Microsoft Account.
When I checked the activation status following the install it showed the Windows 10 Pro was activated. Still not sure if it was tied to my Microsoft Account or not but that was the only common denominator between the clean install below and this one after I wiped out the partitions and laid down an entirely fresh install of Windows 10.
The other way to clean install from a valid Windows 7 or 8.1 system is to use the same media creation tool but instead of creating a USB drive to boot from just select the option to Upgrade this PC now. That will download the Windows 10 ISO and begin the upgrade directly in the current OS.
I then selected to keep nothing from the Windows 7 OS in this case so that meant no settings, files or anything was transferred into the new Windows 10 installation. I was also prompted to go through the entire Out Of Box Experience (OOBE) by selecting my basic settings including logging in with my Microsoft Account.
When I logged into the desktop it was a clean installation of Windows 10 with only my info provided during OOBE there.
This was such a clean install that the Recovery option that is normally available for 30 days after upgrading Windows 7 or 8.1 was not even present.
I then checked the system page and it showed Windows 10 was activated and ready to go.
There is no reason to believe this same process would not work with a properly activated Windows 8.1 system as well.
See the screenshot gallery for a walkthrough of the entire process.
Let us know how your own upgrade situations go in the comments below.