Warning: This should only be attempted by those who are familiar with and comfortable with editing the windows registry. Editing the registry can result in your computer being completely unusable and a complete loss of data. You should always back up your registry before editing!
1. Open Windows Registry Editor by opening the start menu, typing in "regedit" into the search box and pressing enter:
2. Within Regedit, navigate to:
3. Right click in the white space of the right pane and select New > DWORD (32-Bit) Value
4. Set the DWORD value to AllowCortana and verify the value is set to 0, then click OK. The result should appear like so:
5. Close out regedit
6. Reboot your computer, Cortana will now be completely disabled on your computer.