Reason Why You Can't Create "CON" Folder In Windows

"Con" is one of several reserved names that you can't use. Those names date back to the days of DOS, and the reason you can't use them is that have special meanings.You can't make folders on the desktop that have system action or device  references such  as con, nul and prn. Solution is to use another name or use 0 instead of o,O for C0n.
 CON is a reserved name in Windows. It is the name of the Console Device. Actually, this is a lingering remnant from MS-DOS days. In addition to single-letter Device names for disk drives (A:, C:. etc), the other main devices of an IBM PC had reserved names in MS-DOS - PRN for Printer, COM for the serial port, LPT for the parallel port, CLOCK$ for the clock, and - you guessed it - CON for the console (ie the output display).

You will find that you also cannot create a directory called PRN, AUX or COM, either.

If you did manage to create a directory called CON, you'd also find it extremely difficult to delete! Most Windows utilities will refuse to delete a file or directory called CON. This situation arises when someone uses non-standard programming calls to force a directory called CON. Sometimes the only way to delete it again is to reformat the disk.

Read: How To Create CON folder