The Last Version of Windows To Use FAT As The Default File System Was?
Answer: Windows ME
The last version of Windows to use the File Allocation Table (FAT) file system as the default file system of its primary disk was Windows ME.
With the introduction of Windows XP, the default file system used by Windows became New Technology File System (NTFS), which has remained the default Windows file system since.
Bonus Trivia: Although Windows XP was the first consumer-oriented release of Windows to default to to the NTFS file system, Windows NT had NTFS support throughout the 1990s and Windows 2000 Professional, released a year before XP supported (but did not default to) NTFS.