How do I go on developing applications with the Metro UI so that they work on Windows XP/Vista/7 ?
An example for an application is MetroBackUp.
I’m on Windows 7 and have both Visual Studio 2010 and 11 Beta installed.
Is it compulsory to develop them in Windows 8 CP ?
Will they work in other OS ?
Metro apps cannot be developed on OS Windows 7 or less. Metro Apps require WinRT which is in Windows 8 onwards
From the link
Can I develop and debug Metro applications in Win7 with the Visual Studio 11 developer preview?
EDIT
“Metro Style Apps” -> running on Windows Runtime, using Windows 8 UI features (like immersive UI, AppBar, Charm etc).
Metro style apps -> Normal .net apps, having look and feel similar to metro apps. (Example -> MetroBackup
Issue-> Will metro style apps run on Win XP?
They will as long as they do not use any Windows 7 feature (like TaskDialog, JumpList, etc)