For silent uninstall run: rundll32.exe "C:\Program Files\Yahoo!\Companion\Installs\cpn0\ycomp5_5_7_0.DLL",DllCommand uis This will uninstall the toolbar from IE (and add/remove programs) but will not remove any thing from the "Program Files\Yahoo!" folders but they can be deleted, the "s" attached to DllCommand uis will remove the yes/no prompt