(Please ask one question per thread to help people looking for the same things find answers.)
[ol][li] Edit the toolbar and remove the "hideempty" argument from the item which lists the drives.
[/li]
[li] The purpose of checkbox mode is that the selection (checkboxes) used for things like the Copy and Delete commands can be separate from the selection (traditional selection) used by mouse actions like right-click and drag & drop. Checkbox mode exists to let you build up a set of selections for a big task at the end, while still being able to perform several smaller tasks along the way.
Instead of using checkbox mode, you might find a better fit for what you want in normal Details mode (where you can click files with the middle mouse button to toggle their selection without affecting others', like ctrl+left-click but without having to touch the keyboard), or one of the Power mode configurations (where you can have toggle-select on the left mouse button, or various other options).[/li][/ol]