Cortana is a personal voice digital assistant created for Windows 10. With the release of 1503 version, it was working good to some extent. But compared to Siri and Google Voice it still had to go a long way. Also, it's irritating every time it opens a Bing search window, for things it doesn't know. I would love to see something like dictating text in Word, instead of doing web search using Cortana.
Now comes the main point.
Microsoft made sure that it can collect all the personal information, whenever you are using Cortana. In the 1503 version, it was very easy to turn it off. Also you can clear all the personalized data that stored on its servers. But with the Creators update, 1703 version, that easy option was removed. Microsoft made sure that it's consumers struggled hard and give all their information to it. So that it can make more money from its end users.
But just like every hack and tweak the Microsoft community releases to circumvent the problems, Redmond creates. There is also some round-about option through which you can disable Cortana after Creators and Anniversary update. This is for people who want to type in their searches using keyboard and avoid the mic for doing searches. Also this will give you more privacy.
The following 6 methods have been researched over the Internet to disable Cortana in Windows 10 1703 and 1611 version.
Warning: But make sure you surely want to turn it off. Otherwise, it's difficult to enable back it again, though its possible.