You cannot use the following names with regards to files and folders in Windows without manually creating them in DOS using the md command followed by \.\ and then the path to the files/folders to be created. Reserved names: AUX COM1 COM2 COM3 COM4 COM5 COM6 COM7 COM8 COM9 CON LPT1 LPT2 LPT3 LPT4 LPT5 LPT6 LPT7 LPT8 LPT9 NUL PRN You also can’t use Clock followed by other characters with NT4 and older.