Find the Windows 10 ISO file and the activation key.
Find the Windows 10 ISO file and the activation key.
I didn't receive the choice; I was limited to upgrading only. Everything transferred correctly, but I had to install the GPU drivers later. I'm currently typing.
It seems you're referring to a process where you might only have access to one option. You can simply refresh your PC after the Windows 10 installation and remove all files.
It's recommended to perform a fresh installation, since NTFS is upgraded with each Windows update and it's preferable to reformat.
Upgrading from Windows 8.1 to 10 usually lets you choose a fresh install, and your existing key remains valid during the process. A new installation typically removes the old key rather than asking for a replacement.