Which version of window is codenamed the whistler?

Windows XP, codenamed Whistler, is an operating system released by Microsoft in 2001. It is the successor to Windows 2000 and Me, being the first version of Windows NT intended for both businesses and home users. It includes a set of wallpapers, and for the first time, multiple sample pictures and user account pictures too. Its default wallpaper is Bliss, which has become one of the world's most viewed photos as a result of XP's success.

Windows XP was succeeded by Windows Vista in 2006, after years of being in development.