When you insert a CD into your Mac, I wonder what sort of Mac it is and what version of OS X it is using, it should appear on your desktop, assuming you have Finder preferences set to show mounted disks and CD's
Double clicking that should either open it, to view the files, or will launch the installer program.
However, I note you say that your "mac software version is correct" and that your printer is a 7520, but, your use of the term "iDisk" would indicate that your version of OS X is much older than the requirements for this printer.
You must be running OS X version 10.6 or above (Lion and Mountain Lion) to be able to install this printer.
Can you confirm that this is actually what you are running?
My mac will not read the printer driver disk from HP. The printer is a new 7520 and the installation disk is for a windows or mac. My mac software version is correct. It drives me nuts that I can't even look at the disk contents as I do frequently in windows. Is the cd drive called idisk? It won't let me click on idisk and read the cd . Why does it kick it out and not leave it in so I maybe could find an execute file?