I was debugging why Xamarin Android Player could not prepare a VM for me and determined the failure to be in the host-only adapter creation, isolating the problem to this: C:\Program Files\Oracle\VirtualBox\>VBoxManage.exe hostonlyif create 0%... Progress state: E_FAIL VBoxManage.exe: error: Failed to create the host-only adapter VBoxManage.exe: error: Code E_FAIL (0x80004005) - Unspecified error