virtualbox.org

I'm sort of new to VB, everything is running and works perfect. I want to install some software off my ext. hdd but when I go to click "Devices > USB Devices" the ext hdd is grayed out even if I eject the unit in my OS X.

What to do?

OSE does not come with USB support. You need the PUEL version.
You should use the shared folders and transfer the files that way.
See Chapter 4.3. Shared folders in Your VirtualBox users manual.