I recently purchased Windows 8 Pro activation key for 40$. Now, this being a upgrade only license, it wont activate Windows 8 in the case of a clean install. As activation service in Windows 8 looks for any traces of the previous Microsoft OS on the system, when an upgrade only key is being used. In case of a clean install, it obviously fails to find any, hence it refuses to accept your key.
So the correct* way to successfully activate your Windows 8 with the upgrade key would be to first install/have Windows 7/Vista/XP on the computer and then insert your Windows 8 Pro DVD/USB and upgrade to Windows 8 Pro. I was installing Windows 8 on my new hard drive and didn’t have the time to install Windows 7 first. Here’s what I did to activate my Windows 8 with its genuine key in the case of a clean install.
*NOTE: Only follow these steps if you have a VALID Upgrade (I.e.: You legitimately own a licence for a previous version of Windows) Else, according to DRM, it would be considered a sort of piracy.
1. Do a clean install of Windows and during the installation, skip the step of entering the licence key, else simply enter your upgrade licence key.
Once you’re in Windows, you’re going to have to do some tweaking to “trick” it into letting you activate Windows with the Upgrade key.
2. Once you’re at your desktop, run Command Prompt as Administrator (Go to the start screen, type ‘cmd‘. You should see Command prompt on the list. Right-click it and click “Run as Administrator”. Click “Yes” on the Security Prompt).
3. At the command prompt, type: regedit and press Enter.
4. Once in Registry Editor, in the registry tree, navigate to this key: