Windows is not genuine | How to fix black screen

Here is how to fix this windows 7 is not genuine
1. Go to Start Menu.
2.type cmd in search field.
3.Right click Cmd. Select Run as Administrator. It is must to run command prompt with administrator privileges other wise command will not work.
4.Type SLMGR -REARM and press enter.
You will see a windows, Click OK.
6. Just Restart your system

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how to repair windows 7