You can't. DOS Fdisk isn't that great. It looks at Primary Partitions and labels those first. If you HD1 only has one Primary Partition, it becomes C:
If it had more, they would be labeled sequentially. D:,E:,etc...
If your HD1 only has the one Primary, then DOS Fdisk moves onto HD2 and starts labeling there, the first Primary Partition on HD2 becomes D:
Now, DOS Fdisk goes back to drive HD1 and looks for Extended Partitions and labels the Logical Partions. Confused yet?
Here are two examples:
-Basically what you have now-
HD1 (Primary Partition) C:
HD2 (Primary Partition) D:
HD1 (Logical Partition) E:
HD1 (Logical Partition) F:
HD2 (Logical Partition) G:
-What you could have done-
HD1 (Primary Partition) C:
HD1 (Primary Partition) D:
HD1 (Primary Partition) E:
HD2 (Primary Partition) F:
HD2 (Primary Partition) G:
-Or this-
HD1 (Primary Partition) C:
HD1 (Logical Partition) D:
HD1 (Logical Partition) E:
HD2 (Logical Partition) F:
HD2 (Logical Partition) G:
You can ONLY have 4 Primary Partitions on a drive, or 3 Primarys and an Extended with Logical Partitions. You can also have the HD2 with only Extended and Logical Partitions. You might want to think about doing that.
It's kind of confusing, but once you see the scheme, it makes sense. Anytime you add a drive, it's going to look to that drive for any Primary Partitions