Desktop Question:

There are lot of secure option for Windows, You can secure by -

Set a difficult password for administrator
Disable gust account
Give minimum & limit permissions to administrator's members
Make minimum share folder on your Windows's
Give minimum share permission on that folder & full control to trust users
Always change the administrator password
Install third part firewall & set minimum port.
Access & deny those user's & IP which you don't want to access to your computer.
Don't share your password.