If Windows 8.1 is installed but not activated, you can manually enter your key through these steps: Where to buy a windows 8.1 product key - Microsoft Learn

To ensure that Mr. Thompson's computer remained activated, John also provided him with some extra guidance on best practices for managing Windows activations and updates.

If users encounter issues with their product key, they can try the following:

Even Pro edition comes with unwanted apps. Use or CCleaner (free version) to remove:

Many "free" or "extra quality" keys found on forums are pirated or stolen volume licenses . Using these can lead to system instability, lack of updates, or even malware infections. How to Properly Activate Your System