Marcelo,
The dropdown options are displayed in chronological order of when they were created. The only way to change this is to delete and recreate them. If you have added this dropdown field to any screens you should delete these fields from the screens before you delete the field in the table.
In regards to the screen you deleted, first take note of your custom tables and then search for the screens with those exact names in the Customize > Screens tab link. If you cannot find one then it must be the one that you deleted. You can recreate it by basing the new screen off this table. Add a grid object, along with the fields/buttons and actions (i.e. Save All Sections, Delete Active Record, Clear Screen For New Entry, etc.) that you require.
- Jason