When you map a network drive to the Samba share of a VirtualBox PUM VM in order to install (say) the PeopleTools client, the mapped drive may be invisible to your cmd prompt running as Administrator – something you need in order to update the registry and install the client software.
To work around this on Windows 7 through 10, see this article:
https://technet.microsoft.com/en-us/library/ee844140(v=ws.10).aspx