Windows95,98,2000,XP

Windows 95
Originally it was called Memphis, and then Windows 97, but Microsoft changed the name when it realized that it was going to miss its target 1997 release date.
Windows 98 offers support for a number of new technologies, including FAT32, AGP, MMX, USB, DVD, and ACPI. Its most visible feature, though, is the Active Desktop, which integrates the Web browser (Internet Explorer) with the operating system. From the user's point of view, there is no difference between accessing a document residing locally on the user's hard disk or on a Web server halfway around the world.
Windows 98
Originally it was called Memphis, and then Windows 97, but Microsoft changed the name when it realized that it was going to miss its target 1997 release date.
Windows 98 offers support for a number of new technologies, including FAT32, AGP, MMX, USB, DVD, and ACPI. Its most visible feature, though, is the Active Desktop, which integrates the Web browser (Internet Explorer) with the operating system. From the user's point of view, there is no difference between accessing a document residing locally on the user's hard disk or on a Web server halfway around the world.
Windows 2000
A product in Microsoft's Windows line of operating systems. There are four versions of Windows 2000:
Professional -- an operating system for business desktop and laptop systems. It is used to run software applications, connect to Internet and intranet sites, and access files, printers, and network resources.
Server -- both a Web server and an office server. Windows 2000 Server lets users build Web applications and connect to the Internet.
Advanced Server -- an operating for line-of-business applications and e-commerce. It contains all the functionality of the standard version of Windows 2000 Server, plus additional features for applications that require higher levels of scalability and availability.
Datacenter Server -- developed to work in high-traffic computer networks, it is designed for enterprises that need reliable high-end drivers and software. It supports up to 64-way SMP and up to 64 GB of physical memory.
Windows 2000 is sometimes abbreviated as W2K
Windows XP
An operating system introduced in 2001 from Microsoft's Windows family of operating systems, the previous version of Windows being Windows Me. Microsoft called the release its most important product since Windows 95. Along with a redesigned look and feel to the user interface, the new operating system is built on the Windows 2000 kernel, giving the user a more stable and reliable environment than previous versions of Windows. Windows XP comes in two versions, Home and Professional. The company has focused on mobility for both editions, including plug and play features for connecting to wireless networks. The operating system also utilizes the 802.11x wireless security standard.
The "XP" in Windows XP stands for "eXPerience."