Windows® 98 and Windows® Millenium Edition
Windows® 98 and Windows® Millenium Edition are mainly geared towards private users who also want to play games every now and then. Both of these operating systems are capable of running standard applications without problems, and there is a wide selection of programs available.

Links:
http://www.microsoft.com/windows98
http://www.microsoft.com/windowsme

Windows® 2000
Windows® 2000 is another brand-new operating system, with a number of new features targeted at professional users. Windows 2000 should only be installed on new machines with the appropriate processor and memory resources.

Link:
http://www.microsoft.com/windows2000