Authenticate Windows

1.     Ask yourself which type of shop did you go to? Did you go to a shop that sells pirated CDs? The average price of a copy of Windows is normally around US$150. If you bought it at a price cheaper than US$20, please return to the store and ask for a refund. If he does not allow a refund, you are actually being cheated. You need a genuine copy to activate Windows.

2.     Check whether you have typed properly. If you went to an authorized store to purchase your copy of Windows, and you found out that the product key is invalid, make sure you have typed correctly.

3.     Contact your local Microsoft customer service representative. Normally, the phone number is available when you click on the "Yes, I want to telephone a customer service representative to activate Windows now" button in the window. Choose your country name and a phone number will appear. Tell the representative either of these two things.

4. "I have bought a genuine copy but the product key is invalid." The representative will ask of you several questions in which you will answer.
5. "I have used the same CD to install Windows on the same computer for more than 10 times." If your computer caused you lots of trouble, and you are computer savvy, you will use the CD to re-install Windows. But since you don't know the fact that you are only allowed to do this at most 10 times, you may get stuck when the "Invalid product key" error appeared on your screen. The representative will ask you several questions and you will get a new but longer code in which you will use to validate your copy of Windows.
6. Please be honest, the representative will know if you are lying. They ask questions just to test your integrity.