It wasn't clear to me from the OP whether the disk was presently divided into two partitions when one was required, or vice versa. (Or for that matter whether there was existing data files that needed to be retained.
But I suspect it was the former and it was required that it was empty, and so Chuck's suggestion should be fine.
However if it is 2 partitions you require as VHG suggests then Computer Management/Disk Management allows you to change the allocated drive letters anyway.