Formatting an external drive?

Hi all, I have just purchased a "sata" hard drive and an external housing for it, when I plug it into the laptop USB it registers as "mass storage device found" but when I go to "My Computer" (win Xp Pro) there is no drive shown, only the laptop's C & D drives? if I go to the devices manager and click on the "disc drives" it is shown on there and when I double click it shows as device working normally, but when I click on the "volumes tab" it shows as "not initialized" so I assume the drive needs to be formatted?? if so how do I do this???