Pf :P Those names (CON, PRN, AUX, CLOCK$, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9) cannot be used as they are DOS reserved device names...
DOS device names are reserved words, and cannot be used as folder or file names. When parsing a reference to a file or folder, Windows correctly checks for the case in which a single DOS device name is used in the path, and treats it as invalid.
For more info search at microsoft ^^