I have windows XP and any application that creates an icon on the system tray dosen't start up. When I move my mouse over that icon the icon disappears. I tried Reboot and logging on and off and dosen't seem to work. Everytime I run this app (exe) it creates a desktop icon which launches the UI and I am not able to run this application. Can anyone help me in resolving this problem ?

Have you ran antivirus? Any recent hardware or software changes? Can you run these applications another way, say the start menu for example?