MORE INFORMATION
Fast User Switching is a feature that allows multiple users to be logged on to the computer at the same time. Many programs were not designed to run in a multiple-user environment, and would normally have problems when multiple users log on to the computer. To make these programs compatible with Fast User Switching, the Fast User Switching Compatibility service will take one of four different actions when a specific problematic program is being used when user sessions are activated and/or disconnected.
The four different actions are:
Type1 - program can be closed when a second instance is launched. This is the least intrusive action. When a user is using a program and another user logs in and tries to launch the same program, they will have the option to close the original user's instance of the program.
NOTE: This will only work if you have administrative privileges. Otherwise, the original user will need to log back in and close the program.
Type 2 - program is closed when the session is disconnected. This is the most intrusive action. When "Switch User" is initiated or the system returns to the Welcome screen when the screen saver is dismissed, the program will be shut down. A typical example is a DVD player which displays on the screen regardless of the active session. These programs must be shut down for the disconnect to complete.
Type 3 - program is closed on disconnect and restarted on reconnect. This is for programs that use resources that are not easily shared across multiple sessions. A typical example is synchronizing software with a hand held device that uses the COM port while active. The program is restarted when the user reconnects back to their session.
Type 4 - program is closed when another user logs on. This is for programs that do something intrusive, but do not need to be closed on return to the Welcome screen. A typical example is a program that plays music. The program will continue to run when the user disconnects, but will be closed when another user logs on.
To see what programs the Fast User Switching Compatibility service applies these actions to, install Act20.exe from the Support\Tools folder on the Windows XP CD and run the Compatibility Administration Tool. These programs have "FUSBadApplicationTypeX" (where X is 1, 2, 3, or 4) under "Compatibility Fixes."
NOTE: More programs can be added at a later time through Windows Update.
The Fast User Switching Compatibility service uses Shsvcs.dll. Without this file, the service cannot be started.
NOTE: The Themes service and the Shell Hardware Detection service also depend on Shsvcs.dll.
New programs must be compatible with Fast User Switching in order to meet the Windows XP logo requirement. For more information on this, ISVs can download the "Designed for Windows XP Application Specification" document from the following Microsoft Web site: