Hi Jake,
Technically yes, but not sure it is worth all the effort. When you do that, the storage space is called a Volume rather than a Partition.
You can convert a Static (Basic) drive with 1 Partition, the way you have, to a Dynamic drive, where a formatted Volume can span more than one drive, where you can add up to 32 drives in a Spanned single Volume.
You could also start all over, and set up a Striped RAID 0 array. where data is Striped across 2 or more physical drives at the same time. The size here is fixed once you set it up.
If you are needing more storage space, you can just Partition and format the additional hard drive without Windows, just a storage drive, with another Drive letter, or you could "mount" the new drive to an empty folder in "My Documents" and easily have lots of additioinal storage. The Mounted drive would be designated by the folder's name, rather than a Drive letter specification.