REply

Verify Session Switch Notifications:

This task assumes that you have at least two Windows XP user accounts. If you only have one account, create a new account first. 1. Rebuild the project.
2. Run the application.
3. From the Start menu, click Log Off, and then click Switch User.
4. Click the current user name to revert to your previous user session.
5. Verify that you have received WTS_SESSION_LOCK and WTS_SESSION_UNLOCK notifications.
6. Click OK to dismiss both message boxes.
7. From the Start menu, click Log Off, and then click Switch User.
8. Switch to a new user's session, and then switch back to the original user session.
9. Verify that you have received WTS_SESSION_LOCK, WTS_CONSOLE_DISCONNECT, WTS_SESSION_UNLOCK, and WTS_CONSOLE_CONNECT notifications.
10. Click OK to dismiss all message boxes.
11. Close the application.

Go throuught his link:

http://www.pellesoft.se/communicate/tips/tips.aspx?tid=1884

http://support.microsoft.com/kb/310153

http://www.codeguru.com/forum/showthread.php?t=172548