I have a PC with a working Windows 10 Home installatie, upgraded from a Windows 7 Home Premium OS. The harddisk crashed today, so I replaced it with a new HDD and thought: Windows 10 already was installed and activated before so I must be able to install Windows 10 Home from a CD (made with the MS creation tool). During installation it asked for the product key so I typed the Windows 7 Home Premium key from the license sticker. It told me : the key doesn't work. I thought: the setup is not able to check if the 7 key is valid for use in 10 since the setup cannot communicate with the Internet / MS Activation server. So I skipped the key input and continued the installation. When in Windows you can change the product key, so I did (with a working Internet connection): error: the product key is not valid, error: 0xc004f050.
Is there a way to directly install Windows 10 on a system which already had Windows 10 before (upgraded from 7 / 8 / 8.1) OR worst case scenario: you always need to install the original OS, then update the old OS completely and then: upgrade to 10.
If it is: install original OS / update / upgrade then Windows 10 will be the most time consuming MS OS installation EVER.
Also: I would expect a website from Microsoft where you just input the key of Windows 7 / 8 / 8.1 and it tells: already Windows 10 approved OR it generates the Windows 10 key.
Anyone any idea on how to most efficiently do a Windows 10 installation without installing the prior OS?