Microsoft has created a secret Windows XP theme that makes your operating system look like a Mac. Recent Windows XP source code leak Revealed Microsoft’s early work on operating systems and some unreleased themes that the company created during early XP development in 2000.

One is labeled “Candy” and contains a design very similar to Apple’s Aqua interface, first introduced at Macworld Conference & Expo in 2000. The theme is incomplete, but the Windows XP Start button and various buttons and UI elements are clearly themed to match Apple’s Aqua.

Microsoft has never released the Aqua theme for Windows XP and understands that it was used in the early source code of the OS. Windows developers seem to have used themes as placeholders to build the theme engine for Windows XP. The theme itself is described as “Whistler skin with eye candy” and is marked as “internal use only”. Whistler was the codename for Windows XP.

Microsoft has made a famous move to the final version of XP, the blue and green Luna theme. When the OS was first released in 2001, many called it Fisher-Price. The Windows XP theme engine is a major OS update with a third party theme and lots of customizability.

Microsoft was developing Windows XP at a time when there was fierce competition with Apple for desktop operating systems. In the late 1980s, Apple entertained Microsoft with a banner stating “Redmond, let’s get started with copiers” at its annual developer conference. Apple also ran Get a Mac Advertising Campaign Focused on flaws in Windows, especially Windows Vista.

From the 90’s to the 2000’s, Windows was heavily influenced by the classic Mac OS and later OS X. Apple has also borrowed some Windows features, especially windowing, navigation, control panels, and browsing files and folders.

Leaks are a rare insight into the early development of operating systems used by millions of users. I contacted Microsoft to comment on an unreleased Windows XP theme. Update accordingly.