Royan, потому что это зарезервированное слово, такое же как и COM, LPT, AUX, NUL и т.д.
Кстати RTFM 
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File Names in Windows Server 2003
Every time you create a file with a long file name, NTFS creates a second file entry that has a similar 8.3 short file name. A file with an 8.3 short file name has a file name containing 1 to 8 characters and a file name extension containing 1 to 3 characters. The file name and file name extension are separated by a period.
File names in Windows Server 2003 can be up to 255 characters and can contain spaces, multiple periods, and special characters that are not allowed in MS-DOS file names. Windows Server 2003 makes it possible for other operating systems to access files that have long names by generating an MS-DOS-readable (8.3) name for each file. These MS-DOS-readable names also enable MS-DOS-based and Windows 3.x–based applications to recognize and load files that have long file names. When a program saves a file on a computer running Windows Server 2003, both the 8.3 file name and long file name are retained.
Note
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The 8.3 format means that files can have between 1 and 8 characters in the file name. The name must start with a letter or a number and can contain any characters except the following:
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. " / \ [ ] : ; | = , * ? (space)
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An 8.3 file name typically has a file name extension that is from one to three characters long and has the same character restrictions. A period separates the file name from the file name extension.
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Several special file names are reserved by the system and cannot be used for files or folders: CON, AUX, COM1, COM2, COM3, COM4, LPT1, LPT2, LPT3, PRN, NUL.
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Данкинг,  |
