To activate Windows 7, perform these steps:
1. Click the Start button, Right click Computer, click Properties.
2. Under the Windows activation section at the bottom, click Activate Windows now.
3. Choose Active Windows online now.
4. Type your valid Windows 7 product key number, and click the Next button.
5. Windows will verify this product key and activate Windows 7.
6. If the activation is successful, you will see the following window:
7. Now, Windows 7 is activated as genuine.
Generally, if you encounter any Windows 7 Activation problems, check these items first:
1) Internet connection is operational.
2) The activation key is typed in correctly.
3) The current key is not already in use.
I. If all of the above are correct, perform the following steps to reset the activation related components:
a. Click on the Start button and type CMD in the Start Search box. Right click on the Command Prompt shortcut and select Run As Administrator.
b. At the administrator command prompt, run the following commands:
net stop slsvc
Ren tokens.dat tokens.old
net start slsvc
c. Try the activation again and see if it works now.
II. If the issue still persists, contact Microsoft Activation Center to activate Windows 7 by other methods.
How to contact a Microsoft Product Activation Center