Different Operating Systems:

Windows 2000:
Windows 2000 introduced many of the new features of Windows 98 and Windows 98 SE into the NT line, such as the Windows Desktop Update, Internet Explorer 5, Outlook Express, NetMeeting, FAT32 support, Windows Driver Model, Internet Connection Sharing, and Windows Media PlayerNet. Certain new features are common across all editions of Windows 2000.
Windows 2000 also comes with several system utilities. This protects critical Windows system files by preventing programs other than Microsoft's operating system update mechanisms such as the Package Installer, Windows Installer and other update components from modifying them.

Windows XP:
Windows XP is a family of 32-bit and 64-bit operating systems produced by Microsoft for use on personal computers, including home and business desktops, notebook computers, and media centers. The name "XP" stands for eXPerience. Windows XP is the successor to both Windows 2000 Professional and Windows Me, and is the first consumer-oriented operating system produced by Microsoft to be built on the Windows NT kernel (version 5.1) and architecture. It presents a significantly redesigned graphical user interface, a change Microsoft promoted as more user-friendly than previous versions of Windows.