At first, I wanted to add Quantal Quetzal to an external HDD to my dual boot of ML and W7. I already had the iso burned from a previous install to my netbook. I popped in the disc, and it whirred, then made a weird soft and fast clicking noise. To my dismay, I thought it was out of commission after reading forums like this. But, I could hear the drive powering up, as normal, after each reboot. I tried everything mentioned in all the support forums, and nothing seemed to work. But then I saw one thread where a guy suggested doing a cold boot after powering down completely and disconnecting the power source for a couple of minutes (I just powered down my MacBook (late 2009 model) overnight and powered back on in the morning), and presto! The drive worked! I don't believe there's anything wrong with the OS or hardware, other than perhaps something in the BIOS needed the cold boot to sync the DVD drive, again. Until I read that post, I had been doing warm reboots.
Anyways, I hope this helps with getting the drive to work. I also have Windows 7 Ultimate dual booted with Bootcamp. First attempt in Windows failed, but now that it's working in ML, will try again in W7.