Make Window 7 genuine using Command Prompt

Press Windows key + R

Now "run" box will appear , in "run" box type CMD
Click on OK

Note : Must run CMD as Administrator 

Now command prompt will appear

In command prompt type SLMGR -REARM

Wait 5 to 10 seconds.

Now a message will appear in your screen.

Everything is done !!!

Now your Windows 7 is activated.

Restart your PC once. Here after you won't see the warning message that "Windows 7 is not activated"