A recent Windows XP source code leak has revealed Microsoft’s early work on the operating system. Some unreleased themes the company created during its early XP development back in 2000.
The theme is incomplete, but the Windows XP start button and UI elements are clearly themed to match Apple’s Aqua interface. The design was first introduced at the Macworld conference & Expo in 2000.
Microsoft never released its Aqua theme for Windows XP. The theme was used in early source code for the OS. Developers appear to have used the theme as a placeholder.
The theme engine in Windows XP was a major update to the OS. It allows for third-party themes and lots of customizability.