The Oracle VM VirtualBox® User Manual states that VirtualBox is installed into /opt/VirtualBox/, but it is not at that location. I tried
$ cd /
$ sudo ls -lR | grep "VirtualBox"
and also searched for vbox without any luck on either. A search on AskUbuntu just returned a heap of hits on folders shared between the guest and host.
Really, I am just after the Windows 7 guest additions .iso file as you can't download it separately from the Oracle site anymore. Also, how do you install the extensions?
Regards, Hedley