You can perform a “clean” install of Windows 10. Eventually. The basic steps are these:
- Upgrade your previous Windows install to Windows 10
- When the upgrade is complete, run a tool such as ProduKey to find your new Windows 10 key
- Run the Windows 10 install from media (DVD or USB)
- When prompted, enter the Windows 10 key found with ProduKey
Windows will recognize the computer from the previous upgrade and should activate without issue. The Windows 10 key is automatically installed in Windows during the upgrade. I’m not aware of another way to get a key without first performing the upgrade on a valid and eligible Windows install.
This is quick and dirty since the steps are pretty basic. If more detail is needed post a comment and I’ll update the article as needed. Good luck.