Can you describe the exact sequence of events (including any error messages) when you try to boot Fedora?
VirtualBox wiki suggests that Fedora 19 is not supported as a "guest" OS: https://www.virtualbox.org/wiki/Guest_OSes
I do not know whether there is some technological reason why Fedora 19 is not listed, or if simply the list hasn't been updated in a while.
Anyhow, the list in that link may give you some ideas of other "guests" you can try, if you don't have success with Fedora. Good luck!