CentOS

I downloaded centos 7.3 and tried to install on a server(previously there was something installed on it).

When boot up from dvd, I select install centos 7, then it goes to the installation screen.

What is weird is that the Installation source , I could not select , it seems it cant find the installation source.
By right, it should point to the DVD, but it cant find, I wonder why?

First off, 7.3 is not current, 7.4 is and 7.5 is on its way soon (weeks probably).

Which filename did you download to use for this?