Windows XP can hide icons itself. When those college systems use Windows XP: Right-click on the taskbar > properties > Hide inactive icons > customize... > find MSN icon > set it to Always hide.
Only works on Windows XP and you might not have enough rights to do that, but it's the only way i can think of without using any other program.
You could also use a program to hide icons if you have enough rights to install/run a program on the college systems.
Tray Pilot Lite for example is a free program which can do this.
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