Appdata registry key controls the location of application data folder. In Windows XP/2003, the default location of application folder is at C:Documents and SettingsUsernameApplication Data. In Windows 7, it is located at C:UsersUsernameApplication Data. One can change this default location of Application Data by editing the registry key appdata which can be located under the node HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerShell Folders. This registry key is same for XP/Vista and Windows 7.
Appdata is of type string(REG_SZ) and stores the path of the application folder.