By default, Users is listed under Security in the Object List or Database Explorer list. When Security is selected, you will see a Users node listed below, that will show all the users.
To have Users in the list of objects, instead of listed under Security, follow these steps.
1) Select Tools | Options | Explorer | Objects.
2) Find Users in the Name column.
3) In the Category column, delete Security, so that field is now blank for Users.
4) Click OK.
