Is the drive listed when you open my computer? Go to control panel, system, hardware, device manager. Is the drive listed there? If so, right click it, properties, and uninstall it. Reboot your computer, Windows will find the drive, if it is connected properly, and reinstall it. Then see if it works. If not, you might need a new drive, they are not expensive and fairly easy to replace.
I don't know Vista, what I told you is for XP, but maybe the same with Vista..