Do you mean multiple windows within the same session?

Real multiple sessions can only be opened each with their own profile and that doesn't seem likely to me.

If multiple windows are opened via the Ctrl+N keyboard shortcut or via the Firefox or File menu then a possibility is to disable the shortcut and remove the menu entries.

• Customizable Shortcuts: https://addons.mozilla.org/firefox/addon/customizable-shortcuts/
• Menu Editor: https://addons.mozilla.org/firefox/addon/menu-editor/

cor-el

I'm not sure what your referring to and perhaps my verbiage is incorrect in my questioning, so here is what happens. When it locks up she will have in the task bar a multitude of firefox sessions running as a result of double clicking the firefox shortcut whenever she desires to play another online windows game online. I have unchecked the option to open new windows in a new tab. But, I have not found a way to prevent her from opening sever firefox sessions in the task bar.

It would be best to remove the Firefox shortcut on the desktop if she is double-clicking that icon or possibly replace it with a fake dummy shortcut that doesn't do anything. You can try to modify that shortcut to make that a new tab is opened (-new-tab about:blank), but that way you get multiple tabs in one window. There is not much else that you can to prevent opening Firefox windows.

• https://developer.mozilla.org/en/Command_Line_Options