[MP2]

Try and create a file on Windows and name is one of those names - you'll see Windows doesn't allow it.

Here's a quote from Wikipedia:

In addition, in Windows and DOS utilities, some words might also be reserved and can not be used as filenames.[9] For example, DOS Device file:
CON, PRN, AUX, CLOCK$, NUL
COM0, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9
LPT0, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9.

So yeah - don't create any files with those names.