.ITEMDATA-MS File Extension

System file used by the Windows 8 operating system; contains user settings that define the layout of items on the Windows 8 Start screen; arranges tiles for items such as news, weather, Windows programs, and user applications.

Windows 8 stores a file called appsFolder.itemdata-ms in the [user]\AppData\Roaming\Microsoft\Windows\ directory. It also stores a backup of the items data in a file named appsFolder.itemdata-ms.bak.