If you didn't activate your Windows 7 yet, this is the tool you need. Microsoft was so kind as not to counter this exploit. This is the loader application that's used by millions of people worldwide, well known for passing Microsoft's WAT (Windows Activation Technologies). The application itself injects a SLIC (Software Licensing Description Table) into your system before Windows boots, this is what fools Windows into thinking it's genuine.
Here's the download link: Windows 7 Loader by DAZ
First you have to extract the files from the archive.
Then (this is very important): run it as administrator by right-clicking the executable file and left-clicking on "Run as administrator".
Afterward, just click on Install, and let it do its thing. When it offers you the option to restart, please do so by clicking the displayed button.
To check for the operation's success, right-click "Computer" and select "Properties, there you can visualize a brief System Information summary. At the bottom you will see the activation status. Before, it looked like this:
After using this tool and restarting, you should see this:
I'll expand this article soon with more detalied information about using this great tool