With earlier versions of VirtualBox running a Windows guest OS, the Guest Additions installer would start with a single click by selecting "Devices>Install Guest Additions". With Version 4.3.10, selecting "Devices>Insert Guest Additions CD Image" doesn't do anything as far as I can tell; however, the installer is supposed to start according to the VirtualBox web site:
The path to the Guest Additions ISO file in my computer is: /usr/share/virtualbox/VBoxGuestAdditions.isoIn the "Devices" menu in the virtual machine's menu bar, VirtualBox has a handy menu item named "Insert Guest Additions CD image", which mounts the Guest Additions ISO file inside your virtual machine. A Windows guest should then automatically start the Guest Additions installer, which installs the Guest Additions into your Windows guest. Other guest operating systems (or if automatic start of software on CD is disabled) need manual start of the installer.
I'm thinking that VirtualBox is using a different path for the .iso file. Does anyone know where the .iso file should be located so that it can be mounted with the "Insert Guest Additions CD Image" feature?