I recently purchased a Dell. I recently purchased a Dell XPS 420 Desktop computer, running Vista,

Question

I recently purchased a Dell XPS 420 Desktop computer, running Vista, from Dell, including a WD 500GB MyBook external hard drive. The power button did not function from the get-go, but I was able to copy much of my data from my old computer onto the WD disk. Today, when I connected the external drive, the computer "beeped," recognizing the hardware, but it doesn't appear listed on the "Computer" screen. I pulled out the disk's Quick Install Guide, and noted that it does not list Windows Vista among its list of System Requirement. Is there a Vista driver for the disk or can it only be used on my old Windows XT machine?