Actually, now that I look at it, I think we can skip the CD-Extra bit and follow MattD's advice. Try this:
[1] Put in the CD you want to copy
[2] From the main menu choose Recorder > Copy Disc
[3] In the New Compilation window, select the Image tab
[4] Specify a directory and filename for the image Nero will create from the CD
(Nero will create the image)
[5] Put in your blank CDR
[6] From the main menu choose Recorder > Burn Image
[7] Find the image you specified in [4]
[8] Burn away