[CentOS] Centos DVD -

I have been trying to run Centos 6 and 7 in virtualbox on this Fedora23 computer. Actually I also tried Scientific Linux and a DVD copy of Fedora 21 XFCE Live that I had on hand. The Fedora21 works as expected but I seem to be missing something in Centos and Scientific Linux. They boot and run with a text screen but startx reports "command not found" and a ping to other than localhost, reports network unreachable.

So I assume I am missing something. The virtualbox version is 5.0.10 r104061. And Centos was downloaded a few days ago and should be the latest available.

Any help is appreciated,

Bob