Hello.
in the old Machine if you run:
VBoxManage list vms
you will see the VM created have an uuid.
On the new machine, open Virtualbiox gui and see if you have the machine there, if not, try to open the machine file, the *.vbox file
Once the machine is listed, run
VBoxManage list vms
and update this file with the new uuid:
.vagrant/machines/<boxname>/virtualbox/id
example:
.vagrant/machines/prdvbox-racn1/virtualbox/id
Once done.. why you need to keep this machine? Vagrant way is destroy/up all the time :)
Alvaro