Just follow the steps as given below :-
1) Select any file or folder.
2) Right click on it, select ‘Rename’ or simply press ‘F2’.
3) Press and hold the ‘Alt’ key. While holding the Alt key, type numbers ‘0160’ from the numpad.
Note :- Type the numbers ‘0160’ from the numpad, that is, the numbers present on the right side of the keyboard.
Don’t type the numbers which are present on top of the character keys.
4) Press Enter and the nameless file or folder will be created.
Reason :- The file or folder that seems nameless is actually named with a single space.