The host system is a Linux based OS, the guest system – running within VirtualBox – is a Windows based OS. The challange was to share a common folder. The documentation was pretty clear about it; but still it did not work. Now it does. In the guest system, a simple
c:\\>net use x: \\\\vboxsvr\\myshare
did the job . There is no need subsitute vboxsvr with 10.0.2.2 or 192.168.0.2 or something like that. myshare is the name of the shared folder located on the host system.