Here are solutions to some common problems with activation.
Look for your product key on your computer or on the installation disc holder inside the Windows package. If you still can't find your product key, you might have to buy a new one.
A product key sticker looks similar to this:
Go online to see other stickers.
Buy a new product key online now.
There are several reasons why a product key might not be valid:
You mistyped your product key.
The key you typed does not match the key assigned to your copy of Windows.
First, check your product key and retype it. If you're sure that you typed it correctly and your product key is still not valid, you will need to buy a new product key.
You cannot use Windows on more computers than the Microsoft Software License Terms allow. Usually the license terms allow one copy of Windows to be used on each computer. To use the same copy of Windows on another computer, install it on the second computer. You will need to activate Windows again on the second computer. During installation, enter the product key that came with your copy of Windows. If automatic activation fails, follow the screens that walk you through activating Windows by phone. You will have 30 days to activate your copy of Windows.
If you install the same copy of Windows on a second computer and use the same product key that you used to activate Windows on the first computer, you can no longer use this copy of Windows on the first computer. To continue using Windows on both computers, you must buy a new product key to activate the second installation.
You will need to buy a valid product key to activate Windows. To use every feature of Windows, purchase a valid product key and successfully activate Windows within 30 days after installation.
You will see this message if Windows is running in notification mode. To use all features of Windows, select the option on the screen that will best resolve the problem.
Activate Windows online now. If you did not activate Windows within the 30-day activation period, or you typed a valid product key but might have ignored previous activation notifications, select this option to activate Windows on the Internet.
Buy a new product key online now. This option will take you to a webpage where you can buy a Windows product key.
Retype your product key. If you mistyped your product key, or haven’t yet typed a product key, select this option.
Show me other ways to activate. If you did not activate Windows within the 30-day activation period, or you typed a valid product key but might have ignored previous activation notifications, select this option to activate Windows with a modem or by phone.
Also select this option if you made a hardware change that requires activating Windows again and you did not activate Windows within the allotted three-day activation period. Choose to activate by phone.
When you make a significant hardware change to your computer, such as upgrading the hard disk and memory at the same time, you might be required to activate Windows again.
To activate Windows on this computer, do the following:
Open Windows Activation by clicking the Start button , right-clicking Computer, clicking Properties, and then clicking Activate Windows now.
If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
If automatic activation fails, follow the screens that walk you through activating Windows by phone. You will have three days to activate your copy of Windows after changing your hardware.