If Bios does not detect it, it doesn’t exist; as far as your computer is concerned.
Possible lost power to the drive. Possibly the drive firmware is blown. Possibly the the drive has gone south of functional. If the tray opens and closes its probably not a power problem but it still could be.
Its less likely the mainboard hardware and far more likely the drive. If you can pull it out and get it tested it might reveal the problem.
There is [B]no way [/B]you’ll get Vista to show that drive if Bios is not detecting it.