How to uninstall the Windows 10 Free Upgrade update if you don't want it...here's how

1. Open Windows Update by going to Control Panel -> System and Security -> Windows Update, or search for it.
2. Click on Installed Updates on the bottom left corner.
   
3. Locate and select the Update for Microsoft Windows (KB3035583) update under Microsoft Windows section. You can search for KB3035583in the search box on top left corner. 
4. Click on Uninstall to remove the update.
5. Click Yes to confirm.
6. When uninstallation process is completed, restart the computer.
7. Uninstall Update for Microsoft Windows (KB2976978) also if the Get Windows 10 app is not removed completely.

It's now GONE.... Get Windows 10 system tray icon and Windows 10 free upgrade offer reservation nag screen. If you still still have remnants of the KB3035583 update’s files in %WinDir%\System32\GWX folder. In that case just delete the folder (you may need to take ownership of the folder before able to delete it manually.