The default operating system for more than 90 per cent of computer users the world over, this operating system from Microsoft is what most of us use day in and day out. Since the days of Windows 3.1 when it really gained in popularity it has gone from strength to strength and since then we have had Windows 95, Windows 98, Windows Millennium Edition, Windows 2000 Professional, Windows XP Home and Professional, Windows Vista Home Basic, Windows Vista Home Premium and Windows Vista Ultimate. Windows 2000 Professional and its predecessor Windows NT was designed for business users which was later enhanced to Windows XP Professional. In Windows Vista Business, users have a choice of choosing either Vista Business or Vista Enterprise. From Windows 3.1 to Windows Millennium Edition, the operating system was primarily based on the DOS system. From Windows XP the DOS technology used for the earlier operating systems was abandoned in favour of the more robust technology based on the Windows NT technology.