How is the partition of a hard drive made hidden from other user?

There is no option in window OS to hide a partition from other user but using an Utility reg editior can be possible to hide your partition from other user.

I have one wonderfull utility software Name is Tweake UI

Tweak UI is a free user interface customization application. It provides a simple graphical user interface for performing tweaks that otherwise would require editing the registry.

Tweak UI allows you to customise the user interface of the Windows operating system. Users with older, slower computers can turn off many aspects of the operating system's eye candy, such as fading menus, drop shadows, and cursor shadows.

Tweak UI also includes numerous features to customise the way the interface works, such as the taskbar and the desktop. The application also enables you to move the location of their Documents, Music and Pictures folders, as well as other system folders. It also includes various tools to repair elements of the operating system, such as icons, hot keys, the font folder, and file extension associations. It can be used to disable AutoPlay, archive partition on one or more drives as well.

hide partition can be possible from this utility program

Basm Allah Alrahman Alrahim

you can hide partation from windows -> start ->control panel -> administrative tools ( if view by category you must choose  system and security1st) -> computer mangment -> storage -> disk mangment ( then chose the partation -> click right -> choose change drive letterand path -> remove

read this article for more information

and this2

but if you really to compleatly hidden your Partation you must use any partation program like Mini Tool go there is a vedio to learn fast