Most of the time when it comes to mounting cdroms or mounting issues is that your default user just needs to belong to a certain group.
Like a 'audio' group, or a 'cdrom' group. Linux-based operating systerms were designed from the ground up to be multiuser. So if you have users accessing the computer thru ssh or telnet over the internet, and you have a few hundred to deal with.. then it may not be a good idea to let them all use the cdrom drive.
So the OS usually has default groups that it assigns to certain aspects. Like access to the cdrom and such. It's a different mentality from windows... your kinda expected to figure this stuff out yourself rather then have everything be open by default and possibly cause a security risk...
With Mandrake and Ubuntu and such you have forums you can go and get help.. these groups permissions and other small problems tend to be very distro specific and you'd probably get the most accurate help by visiting their respective forums or irc channels.
Also if you go to places like what I have in my 'sig' with those guides it will help you understand what is going on much better and allow you to 'get under the hood'. Most Linux distros require a bit of tweaking to get it to work exactly how you want them to. It's one of those things that people point out when they talk about how 'linux is not ready for the desktop' type things. Doesn't bother me much personally, though. Once it works it works.