Windows 98 was a rehash of Windows 95, as was Windows ME. Windows 2000 was a good desktop OS, based on Windows NT, but many of the crappier 16-bit apps wouldn't run, so it wasn't much used by home users. Windows XP was Windows 2000 with a lot of Windows 95 kludged back in so that old 16-bit apps would run and the user experience looked more like Windows 95.