Well, that would probably be /
But that's not the way to access your drives, you have to mount them first, and then depending on where you did that is where you'll access the data.
Just to get things rolling, I'll shoot you through this, then you should read some of the links in my sig, and check out the tutorial over at www.linux.org
Ok, so mounting CD's:
Login as root and enter your graphical environment.
Open up a console (probably an icon in the "taskbar" that looks like a small computer screen)
And now insert your CD into your cdrom device.
ls -l /mnt
(LS -L lowercase)
Do you see a directory called cdrom? If so, don't do the next step, if not:
Now we are ready to mount the cd:
mount -t iso9660 /dev/cdrom /mnt/cdrom
Now to access the data, either open up your gui filemanager (probably if you are in KDE it will be konqueror, so you can just go to run and type konqueror)
And make your way to the /mnt directory. / is the upper most directory in the tree so if you can get there, you can go anywhere from there. Follow the links, so go / then see the mnt click it, see the cdrom, click it, now you are in /mnt/cdrom
Ok, I hope this has helped. I went back through and bolded everything that you should type, so you can decipher from my explaination and the text that should be typed.