DVD-rom not recognised

I have just realised that my Dvd-rom has dissapeared and is no longer listed in the drives in My Computer, I must admit I havent used it for a while and have loaded various things on my computer in the last few months.
I am running XP home. and the DVD rom is a Sony DDU1612.
Does anyone have any clues as to how I can get it back????

What does device manager show? (right-click "My Computer", choose "Properties", then "Hardware" then "Device Manager"

Does the BIOS list it upon bootup when scanning for drives?

Does the drive door even open? - My first thing to check would simply be for loose cables.