Right-click the folder (create it if it doesn't exist), select New > String Value . Name the value serialnumber . Leave the value data blank and restart the game. Alternative Troubleshooting Steps
Right-click the game's .exe file and select Run as Administrator to give it permission to read/write the registry.
Ensure you are entering characters in UPPER CASE and including all dashes as shown on your code.
Serial keys are case-sensitive and full of characters that are easily confused (e.g., the number 0 vs. the letter O , or 1 vs. I ). Even a single wrong character will trigger the error.
Ensure the key matches the specific edition (e.g., Gold Edition vs. Standard ). For Legacy Retail Discs