Can't assign previous drive letter in Windows 7

I had an internal 1TB WD drive that was in need of an RMA which I processed and received the new drive for. I proceeded to wipe my old drive, power down the machine and remove the drive, and swap the new one in. Wanting to keep things consistent and the same as the way the previous drive was in the system, I went to Disk manageent within Windows 7 and attempted to format the drive and assign the same drive letter (H) that was previously associated. However, when I attempted to do so, “H” wasn’t an option.

Thinking it might have been hung somewhere, I followed this guide to remove the H key from the registry:

However, that still didn’t work and H isn’t an option to reassign to this drive. Does anyone have any insight as to how to correct this?

Have you also tried changing the drive letter without formatting the drive?

This article shows how to accomplish that: