No user serviceable parts!
When Apple say there are no user serviceable parts in an iMac they mean it!
Not because you can't change them but because you can't get anything out without spending a week taking it to bits.
Worst layout ever!
For those who are interested, there was just one cd in the drive, which was stuck on something, but the something seems to have moved after I spent an hour and a half trying to extract the drive. Sigh, I wonder what it could be, as the cd was definately not ejecting (I'm not daft, you don't open an iMac unless you have to!).
Next time I'll just send it away to be fixed.