Thanks for the advice, both of you: however, I do find it incredible that Apple can sell a computer with a combined CD/DVD drive that won't burn CDs from one of their own programs, i.e.Itunes, and that I might have to buy additional software, when I've only just bought the machine that was supposed to do everything! (And looking at the Apple forums, it does seem to have been a frequent and ongoing problem for Mac users).
I'm going to see if the "Genius Bar" can fix it tomorrow, as it's still under warranty.