Windows Millennium Edition (ME) was released in 2000 as the successor of Windows 98 SE.
Many new features were announced by the people from Redmond. Among these were improved Universal Plug 'n Play, or UPnP, System Snapshots and System Restore, and automatic Windows Updates from Microsoft's website. These were exciting new features at that time, almost unbelievable in how futuristic and advanced they sounded.
However, things did not work out exactly as expected. Early adopters had problems with basic installation. It seemed that one needed to be both clever and lucky just to complete the installation. One also needed to luckier still to have all the PC's hardware work properly. This was due to a security decision made in ME: drivers for non-Plug 'n Play devices were not allowed to be installed. This resulted in huge compatibility issues. A large number of users were unable to get their hardware working correctly, and the system might crash several times per day or week. If one were fortunate enough to have a system that would run somewhat reliably, the fun was not over because the system might simply refuse to shut down.
These problems lasted for years and some were not addressed until Windows XP was released. It was so bad that Millennium Edition’s abbreviation ME was popularly said to stand for “Mistake Edition.”
Was ME all bad? Actually, no. Millennium Edition introduced many features that are still in use today (albeit improved): automatic updates, system file protection, system configuration utility, system monitor, Windows Movie Maker, Windows image acquisition, image preview, Home Networking Wizard, improved power management, compressed folders, on-screen keyboard (which was also present in Windows 3.1), generic drivers for USB mass storage devices, and the TCP/IP stack which was implemented from Windows 2000 code. (Windows 2000 was part of the separate Windows NT line. Windows 9.x and ME were eventually merged with the NT line to become Windows XP.)