The previous answer is unlikely to work because Cortana keeps searchapp.exe running all the time (causing cpus to get hot).
The following commands worked for me. You have to paste them into in Administrator-level Command Prompt again and again until the timing is right and the "move" works.
cd %windir%\SystemApps
taskkill /f /im SearchApp.exe
move Microsoft.Windows.Search_cw5n1h2txyewy Microsoft.Windows.Search_cw5n1h2txyewy.old
Optional: to remove Cortana completely (in addition to stopping searchapp.exe), run the following command in Administrator-level Powershell:
Get-AppxPackage -allusers Microsoft.549981C3F5F10 | Remove-AppxPackage
David Spector
Springtime Software