The internal drive will mount and read the things when not owned by Parallels. What's weird is that the firewire drive sems to have NO problem with the same discs.
Connor4DJ, where do you want to read cd/dvd? In the guest OS? What kind of guest OS? Or you want to read cd/dvd in OS X while Parallels running?
Well, all you need is to disconnect CD/DVD drive from running virtual machine. You can connect it back to VM at anytime.