Microsoft created a secret Windows XP theme that made the operating system look like a Mac. This discovery was made thanks to a recent leak of Windows XP source code.
Thanks to the leak, information about the early stages of OS creation became available. In particular, several topics were declassified that Microsoft created during the development process and subsequently did not release it to the people.
One such theme is called Candy and includes a design that closely resembles the Aqua interface, first presented by Apple at the Macworld Conference & Expo in 2000. Although the theme is not complete, the Start button, some other buttons and interface elements are definitely the same as the Apple Aqua.
Microsoft never released this theme for Windows XP. Apparently, Candy was used by developers while debugging the OS theme engine, as it is marked as “internal use only”. The theme was described as Whistler skin with eye candy, while Whistler was the codename for Windows XP.