Windows XP dropped in October 2001 and instantly became the go-to operating system for pretty much everyone. It combined the stability of Windows 2000 with the home-user friendliness of Windows ME—except it actually worked. The interface was colorful, smooth, and didn’t crash every other hour. XP brought in fast user switching, better wireless support, built-in CD burning, and a Start Menu that finally made sense. Service Pack 2 in 2004 tightened up security and made it even more solid. Whether you were gaming, working, or just burning mix CDs, XP was the OS that stuck around—some people kept using it well into the 2010s. If you remember that startup chime and the green hill wallpaper, you already know.