Esto es lo que te respondí en otro foro (por si no lo llegases a ver):
ya he comprobado que no me aparezca en los programas
La solución no es ocultarlo, sinó desinstalarlo. ¿Te refieres a la barra de programas de Firefox, o en la lista de programas instalados de Windows?
De todas formas sigue los pasos oficiales de desinstalación de IMVU:
http://imvuinc.ourtoolbar.com/help/How do I uninstall the IMVU Inc toolbar?
Firefox users
In the Firefox browser menu, select Add-ons > Extensions.
Select the IMVU Inc Community Toolbar.
Click Remove.
How do I enable or disable the search page that appears when I open a new tab?
Firefox users
Open the toolbar's main menu (by clicking on the arrow immediately to the right of the toolbar's logo).
Select Toolbar Options and then click the Additional Settings tab.
Select or clear the check box next to: "Show a search box on new browser tabs."
How do I remove the IMVU Inc toolbar's customized Web Search?
Firefox users
Open your browser's Search Engine menu (upper-right corner of your browser) by clicking the arrow.
Choose Manage Search Engines…
Select IMVU Inc Customized Web Search.
Click the Remove button, and then click OK.