Just use DISKMGMT.MSC to change the drive letter of your DVD drive, say to N. You can of course change it to anything you want that is not currently in use, temporarily or permanently. You can then re-change it to anything else you want later, if you just want to "permute" your existing HDD/partition and DVD drive letters.
Once D is now N, so that D is now available, you can change any other drive/partition you have to D... or again, any other available letter that is not currently being used.
You can also create more than one partition on hard drives, and again temporarily (or permanently) change the Windows-assigned drive letter to anything else not currently assigned so that through a series of "change drive letters" you can create whatever drive/partition lettering scheme you care to invent.
I have multiple desktop and laptop machines in my home environment, and I try to keep things as identical as I can on each one no matter how many internal or external HDD or DVD drives I have on each machine. This is for my own convenience, and making it easy for me to move from machine to machine and not have to remember what the particular internal/external drive configuration I have. I also create the same collection of multiple partitions (each of which gets a "drive letter") spread across however many physical drives I have... again just so that if I'm used to having some particular data folder on a particular drive letter on one machine, I will immediately know it's on the same drive letter on any machine.
So, for example, I letter my CD/DVD drives as N no matter what machine. My internal hard drives on all machines are always lettered with partitions C through K, with L and M available for internal card reader drives, or additional hard drive partitions if appropriate. My external USB 3.0 backup drives on all machines are from Verbatim (2TB Store 'n' Save") and I letter them V on all machines.
I "share" all of my drives on all machines on my WORKGROUP (which all machines are part of). So I can get to any drive on any machine from any other machine. And if I want to permanently assign a drive on one machine as a "network drive" from another machine, I always start with P, Q, R, etc, as the network drive letter for C, D, E, etc. hosted on the remote machine. So no matter what machine I'm sitting at, I know that P is actually [network mapped] C on the remote machine, Q is actually D, etc.,... again just to try and simplify things for my memory and not to require a paper roadmap of how each machine is configured. They're all configured the same way, and they all use the same drive partitioning and lettering conventions.
Same goes if I build a new machine or add drives or change hardware or whatever. Each one looks like the others, including using DISKMGMT.MSC to re-letter things to my liking no matter what the hardware and Windows did when the machine first powered up.
For example, I just "built" a new Lenovo M93p machine for my brother-in-law. It came with one 1TB internal hard drive, which obviously was C when the machine first powered on. It also had a 12GB "recovery partition" from Lenovo for potential use to restore the machine to "factory" if necessary, and that partition had been lettered Q. And the CD/DVD drive had appeared as D on frst use.
Well, I wanted to install a new 256GB Samsung SSD drive, carving out two partitions on it one of which would be the Win7 C, and the other would be D for DATA. And the plan was to repurpose the original 1TB drive as a second data drive, with four partitions E, F, G and H. And I was adding another Verbatim 2TB external USB 3.0 drive or backup... which I wanted to be V.
I used Macrium Reflect Standard to create an image of the initial "100MB system reserved" and C (Win7 partition from Lenovo) onto the external Verbatim drive, and then used Macrium Reflect to copy those two images back from the USB drive to the front of the SSD (which up to that moment was simply a second internal drive to Windows, with no partitions on it).
Then I booted into the BIOS, and changed the boot sequence of the machine, to be CD/DVD first before SSD. Then I booted to a standalone CD version of Partition Wizard, which I used to (1) set the new "system reserved" partition on the SSD to be "active", (2) resize/shrink C on the SSD down to 100GB, (3) create the remaining space on the SSD to be what would be D, (4) delete all partitions on the 1TB hard drive, and (5) create four new partitions which would be E, F, G and H.
With that done, I then rebooted back to Windows (from the SSD now, as the SSD was the first boot hard drive in the boot sequence) and looked at what had resulted from Windows' perspective, with all of this drive rearranging and partitioning. Well, aside from C on SSD getting to be C in the new arrangement, pretty much nothing else ended up lettered as I really wanted.
So I then proceeded to do just as I described earlier... namely to just use DISKMGMT.MSC to "permute" the drive letters until I got what I wanted. In the end, the SSD had C and D, the HD had E, F, G and H, the CD/DVD was N, and the Verbatim external USB 3.0 drive was V. And Windows was now operational on C from the SSD, with the 1TB hard drive wired exactly as it was from Lenovo but simply dropped in the BIOS boot sequence below the SSD so that it really is now just a "data" drive.
You can letter things any way you want. You don't need to re-cable things, as you can accomplish the same result in the BIOS (if you need to promote any new drive to be the first boot drive in sequence), as long as you make sure the "active partition" (i.e. the "system reserved" partition where Boot Manager lives) is on that first boot drive per the BIOS. Then, once you bring the system up and see what drive letter arrangement Windows and the hardware came up with (depending on which motherboard SATA sockets you used to cable your drives into), you simply then re-letter each drive/partition to your liking... permuting as you and, and temporarily re-lettering to any unused letter so that you can get each partition eventually lettered as you want.
