[CentOS] DVD reader: Hardware problem or OS glitch?

Hello: The box is  dual boot (Win XP & CentOS 5). A Dell Dimension
4300 Celeron. There was an intermittent problem with this last year
and last Thanksgiving, I wiped the HD and installed Win XP and CentOS
5 clean. My daughter asked me to install KStars which is in the kdeedu
RPM on the Fedora Core 6 Install DVD. I did that, without any
problems, on my box and on my wife's box. On the Dimension 4300, in
Linux, the OS thinks the DVD ROM is empty. I suspect this is a HW
problem, but: (a) Windows can see everything on the DVD, without any
problem and (b) I can boot the Fedora Core 6 Install DVD, without any
problem. If anyone on the ML has ideas about what might be wrong with
the installation of the OS (I have GNOME and KDE installed and the
problem is the same with either desktop) please give me your
suggestions about how to get the DVD to mount properly. TIA!