If you want to create an undeletable Folder you must remember that you cannot create undeletable folder in your root directory (ie. where the windows is installed). That means if your windows is installed in C-Drive you can't create this kind of folder in C-drive. You can try in another drives like D, E or any other.
  • Go to Start and then Click on Run.
  • Type cmd & hit enter (To open Command Prompt ).
  • Remember you cannot create Undeletable & unrenamable folder in your root directory (i.e. where the windows is installed) That means you can’t make this kind of folder in C: drive if you installed windows on C:
  • Type D: or E: and hit enter
  • Type md con\ and hit Enter (md – make directory)
  • You may use other words such as aux, lpt1, lpt2, lpt3 up to lpt9 instead of con in above step.
  • Open that directory, you will see the folder created of name con.
  • Try to delete that folder or rename that folder windows will show this error message.
HOW TO DELETE THAT FOLDER ?

It is not possible to delete that folder manually but you can delete this folder by another way mentioned below.
  • Open Command Prompt. (Start -> Run -> type cmd)
  • Type D: ( if u created this type of folder in D: drive) & hit enter.
  • Type rd con\ (rd – remove directory)
  • Open that directory and the folder will not appear because it is removed.