Use Disk Management / Change letter to shuffle the disk letters on each system to look the way they used to do. It will let you change everything except the "system" "boot" and "page" partition(s), which are probably C:
Everything else, including your CD-ROM, flash drives, USB camera connection, card readers, etc, you can change to anything you want. The apps must be changed to the same letter as they were when you installed them, otherwise they won't work.
It's good practice to set these letters yourself whenever you install an OS, before you start installing other software, rather than let the system set default letters at boot.
As you can see, letting the system set letters dynamically seems to be stable but in reality the whole system can suddenly shuffle if you add a PCI card, or a new HDD, or even just recable things differently.
Luckily, since XP, it is under your control.
W95 - WME were a nightmare if you added a HDD, everything changed (and was not able to be changed back)