Disable Cortana Using Group Policy Editor

To disable Cortana in windows 10

1. Press Win + R keyboard accelerator to open Run dialog box.
2. Type GPedit.msc and hit Enter or OK to open Local Group Policy Editor. Navigate to Local Computer Policy -> Computer Configuration -> Administrative Templates -> Windows Components -> Search.
3. In the right pane, double click on policy named Allow Cortana.
4. Select the Disabled radio button.
5. Restart the PC and Cortana and Bing Search will be disabled. (May work after signing out and in again)
   
   
   
   Source: https://superuser.com/questions/949569/can-i-completely-disable-cortana-on-windows-10