The reason why this error occurs is that you are not using a genuine copy of Windows 7 OS.The main reason why people opt for not genuine copy is because Windows OS is priced very high.
People don't want to spend this much money for an OS.
Why Should You Remove This Error
The reason's why you should remove this error because it will leave a watermark showing that your Windows is not genuine. When you start your PC it will show Windows is not genuine.If you are a laptop user due to this error your battery performance will decrease.So this error is a headache to users.
How To Fix The Error
Follow these steps:
Step 1:Click on the Start button and search for Command Prompt. Right click on Command Prompt and click on Run as administrator.
Step 2:Once Command Prompt window is opened, type “SLMGR –REARM” command and hit Enter.
Step 3:As you press the enter button, a popup will appear with a message that command completed successfully. Click on OK to close it. Now close the Command Prompt window and restart your PC.
Once your PC is rebooted, the Windows is not genuine error will be gone from the PC.