Download the tool called win6x_registry_tweak. Now open a command prompt with admin rights in the foldera command prompt with admin rights in the folder of the downloaded exe and run this command:
install_wim_tweak.exe /o /c Microsoft-Windows-Cortana /r
This command removes the 3 cortana packages (Cortana main package, language pack and PAL package):
Microsoft-Windows-Cortana-Package~31bf3856ad364e35~x86~de-DE~10.0.10240.16384
Microsoft-Windows-Cortana-Package~31bf3856ad364e35~x86~~10.0.10240.16384
Microsoft-Windows-Cortana-PAL-Desktop-Package~31bf3856ad364e35~x86~~10.0.10240.16384
After a reboot your Windows is cortana free.
ATTENTION. Make a full backup if you later when to restore it to get Cortana back. If you have not done any backup, use those steps to generate the CABs for your Buildthose steps to generate the CABs for your Build. Replace Flash with the MUM names of the Cortana packages. You need to generate CABs for all Cortana MUM files like here the x86 MUMs for Build 14393 
.
