VBox: how can a guest check the underlying version of VBox?

Hello list,

I' apologize for bothering this list with this "non-CURRENT" question, but I
hope I can find here a quick answer.

From within a running guest I need to check what Vbox version is running the
guest to provide a deployment system with the necessary informations about the
Guest Tools to be installed. The primary "Guests" are Windows 7 on top of
FreeBSD as the host and vice versa, Windows 7 as host and FreeBSD as guest.

Thanks in advance,

Oliver