User Profile Namespace in Windows XP

In Windows XP and Windows 2000, the user profile namespace is characterized as follows:

• Local user profiles are stored within the root folder %SystemDrive%\Documents And Settings.
• Each user who has logged on at least once to the computer has a user profile folder named after his user account. For example, user Karen Joe (karen@live.com) has the user profile folder %SystemDrive%\Documents And Settings\karen; the local Administrator account has the user profile folder %SystemDrive%\Documents And Settings\Administrator; and so on.
• A special profile folder, %SystemDrive%\Documents And Settings\All Users, contains common program items, such as Start Menu shortcuts and desktop items that are accessible to all users who log on to the computer. By customizing the contents of the All Users profile, you can provide all users who log on to the computer with access to programs and shortcuts that they need, in addition to those items within their own personal Start Menu and Desktop folders. The All Users profile does not contain a registry hive because Windows does not load this profile. Instead, Windows writes all shared settings to the HKEY_LOCAL_MACHINE hive of the registry on the computer.
• A special hidden profile folder, %SystemDrive%\Documents And Settings\Default User, is used as a template for all new local user profiles created on the computer. When a user logs on to the computer for the first time and no Default Domain User profile is stored in the NETLOGON share on domain controllers (and no roaming profile is already stored in a network location for users with a roaming user profile configured), the Default User profile is loaded and copied to %SystemDrive%\Documents And Settings\user_name as the user's local profile. If a Default User profile is stored in the NETLOGON share, this profile (instead of SystemDrive%\Documents And Settings \Default User) is copied to %SystemDrive%\Documents And Settings\user_name as the user's local profile.
• %SystemDrive%\Documents And Settings\LocalService and %SystemDrive%\Documents And Settings\NetworkService are two special, super-hidden profile folders automatically created for the LocalService and NetworkService built-in accounts used by the Service Control Manager to host services that don't need to run as LocalSystem. Windows requires these special profiles; you should not modify them.

The hierarchy of folders (the namespace) within a user folder on Windows XP consists of a mix of application settings folders and user data folders, many of which are hidden. Some of the important folders in this namespace include:

• Application Data Contains application-specific data, such as custom dictionaries or vendor-specific data. The directories inside Application Data are roamed between computers.
• Cookies Contains Windows Internet Explorer cookies.
• Desktop Contains desktop items, including files and shortcuts.
• Favorites Contains Internet Explorer favorites.
• Local Settings Contains application settings and data that are either computer specific or are too large to roam effectively with the profile. (The directories inside Local Settings are not roamed between computers.) Subfolders of this folder include Application Data, History, Temp, and Temporary Internet Files.
• My Documents This folder is the default location for any documents the user creates. Subfolders of this folder include My Pictures, My Music, and other applicationspecific folders.
• NetHood Contains shortcuts to My Network Places items.
• PrintHood Contains shortcuts to printer folder items.
• Recent Contains shortcuts to files, programs, and settings used recently.
• SendTo Contains shortcuts to document storage locations and applications.
• Start Menu Contains shortcuts to program items.
• Templates Contains shortcuts to template items.

In Windows XP, user profile folders such as My Documents and Favorites are known as special folders. These special folders are identified to the operating system using constant special item ID list (CSIDL) values, which provide a unique, system-independent method for identifying folders that are used frequently by applications but which may not have the same name or location on any given system because of the installation method or Folder Redirection.

The implementation of the user profile namespace in Windows XP has several disadvantages:

• A user profile consists of a mixture of application and user data folders stored at the root of the profile. This means that the user profile provides no clean separation of user data from application data. For example, the %SystemDrive%\Documents And Settings \user_name\Local Settings\Application Data folder contains either computerspecific data and settings that cannot (or should not) roam with the user's profile, or it contains data and settings that are too large to roam effectively. (They would delay the logon experience if they were roamed.) On the other hand, the %SystemDrive% \Documents And Settings\user_name\Application Data folder contains data and settings that should roam when RUP is implemented. This confusion of having roaming and non-roaming data and settings stored in two similarly named folders sometimes leads to third-party vendors creating applications that store their data and settings in the wrong folder, affecting the ability of these applications to roam along with the user who uses them.
• My Pictures, My Music, and My Videos are subfolders of My Documents even though they are designed to contain media files rather than conventional documents. This makes configuring Folder Redirection unnecessarily complex and sometimes leads to nondocument, user-managed data being unnecessarily redirected.
• No guidelines or restrictions exist for how third-party applications should store their per-user settings and data within the user's profile. For example, third-party applications might create new subfolders of the user profile root folder for storing per-user information instead of storing it within existing folders in the namespace. Third-party applications also sometimes combine computer-specific and per-user settings within the Application Data folder, which can make it difficult for certain applications to roam when RUP is configured.
• Users have no simple and intuitive way of securely sharing portions of their user profiles and the data they contain with other users to access over the network. This makes it difficult, for example, for inexperienced users to share specific documents within their My Documents folders.
• The system of using CSIDL values to identify special folders has several disadvantages. For example, CSIDL values could not be extended, which means that application vendors could not add their own special folders to user profiles easily. In addition, no application programming interface (API) was available on Windows XP for enumerating all CSIDL values available on the system. Finally, under the CSIDL system, only the My Documents folder could be redirected to a different location.