I have a CPU that I put together myself. I'm far from a PC expert though. I put a new HD in. It's connected by SATA. It shows up as the G drive on my computer.
The problem is, when I drag files from anywhere on my C drive onto the G drive, a copy of the file is made on the G drive and the original doesn't move. I want the files to move like they would if you drug them from one folder on the desktop to the other.
As wintermint has mentioned, when you just drag files from one drive to another it will make a copy. This is helpful in ensuring you don't lose any of your originals when transferring files say onto a USB drive or when burning a CD etc.
If you really don't want them on the source drive, then you will have to cut + paste. If you don't feel like right-clicking a bunch, you can always use CTRL + X to cut the source documents, then CTRL + P to paste them onto the destination drive.
The thing that surprises me is that you say it doesn't happen when you move from C: to F:. The standard behaviour for Windows Explorer when dragging a file from one drive to another is to copy, not to move. Windows Explorer moves by default only if you copy a file from one folder to another on the same drive.
If you want to force a file to be moved rather than copied when you drag it from a folder on one disk to a folder on another, hold down the Shift key as you drag it. If you want to force it to be copied when you drag between locations on the same drive, hold down the Ctrl key as you drag it. While dragging a file you'll see the mouse pointer icon change when you press these keys to show whether it's copying or moving.