You can sometimes find unused OEM or "System Builder" retail packages on sites like Amazon or through specialty software vendors. Prices for these can range from approximately $50 to over $100 depending on the edition (e.g., Professional or Ultimate).

If Windows 7 is currently installed and activated, you can use tools like Belarc Advisor or ProduKey to retrieve the key from the system registry.

Some licenses are specifically sold for refurbished PCs and may be available at lower costs, often around $50.

Once you have a valid 25-character key, you can activate it by: Right-clicking and selecting Properties . Clicking Change product key at the bottom of the window. Entering your key and following the prompts.

You can try running the command wmic path softwarelicensingservice get OA3xOriginalProductKey in an elevated Command Prompt to see if the key is embedded in your system's firmware. Activation Steps