[H] icon I can not find!

[DHSinclair]

This is WinXP-sp3.
I have this system tray icon, "Windows Messenger-Not Signed In."
It will not tell me where it comes from............ :(
Pops up on the taskbar each time I reboot.
Can I kill this; or, just make it stop/go to sleep?
I have already stopped the Messenger Service in AdminTools/Services.
Thanks,
Duncan