DVD drive not reading CD's?

The dvd drive on my laptop only reads dvd's and doesn't recognise cd's at all. I have a Sony N11S/W. I called up comet today as i have an extended warranty on it and asked about it and they said it is probably a software problem and that i would have to pay �25 for it to be fixed as the warranty is only for hardware problems!! I find that an absolute joke that i have spent �250 quid on an extended warranty and i still have to pay for it to be fixed! I don't understand how it can be a software problem when it is the dvd drive (hardware) that is at fault! Does anyone have any ideas what is the problem and if it is actually software related?