|I have no real experience or familiarity with Vista but presume that it has disk (or drive) management similar to XP?|
Presuming it has... then use that reconfigure the drive as you wish it to be.
Presumably you want to have more than a single partition (which is a good way to configure a large drive - makes it easier to find data; also easier to defrag etc...)?
At present if you have already formatted it as it came then you have a single partition? If so then via disk/drive manager - access the drive and delete that partition; then repartition as you wish it to be and format. A least two partitions would be my minimum.
Be sure you address/access the external drive - for obvious reasons...