I have installed VirtualBox in order to use Windows 7 as guest on a Macbook Air running Mavericks (mainly to be able to use a printer that has no drivers for Mac). Also, I have installed the Oracle_VM_VirtualBox_Extension_Pack and the Guest Additions, so that now the video settings as well as the support for USB are available. Except that, while the flash drives as well as the printer work, the external HDD drives connected by USB do not.
After un-mounting the external HDDs in Finder they appear only greyed out in VirtualBox system tray.
Adding them as filters in the Settings of the Virtual Machine makes them look selected as they should (no longer greyed out), but they are still not available in the guest Windows.
I am talking about two external HDD drives, both 500 GB, one ntfs and one fat32.
I expected the USB connections to work fully after installing the Extension_Pack and the Guest Additions, but it looks like there's something more to be done.