Windows today is not quite as unified as people tend to believe. Even though it is outdated and obsolete, Windows 98 SE is still the most commonly used operating system in the world. Many Windows 98 and 2000 users have not upgraded to Windows XP because they do not see enough benefits to outweigh the steep cost. Almost all new computers purchased today come with Windows XP installed. Microsoft has firmly established their line of operating systems as the world leaders, but they haven't succeeded in getting all of their users to upgrade to XP. Microsoft's hold in the server market is not as strong. UNIX is a serious competitor and is used more often than Windows products on critical servers. Microsoft also receives server competition from Novell NetWare and Linux.