Final answer:
Windows Server 2008 is not available as a desktop operating system.
Step-by-step explanation:
The correct answer is 5) Windows Server 2008. Windows Server 2008 is not available as a desktop operating system, but rather as a server operating system. It is designed to provide services to multiple clients in a network environment, while desktop operating systems like MS-DOS, Macintosh OS X, Windows 7, and Linux are specifically intended for personal computer use.