if it is a Card reader, physically disconnect it from your PC, after its shut down.
reboot, start up, if the CD drive doesn't get reassigned to drive D, then use Computer Management/Disk Management in Windows and Reassign Letter D to the CD Drive, save/apply things, reboot, check to make sure it took, once it has, shut down, reconnect card reader, and reboot, should assign card reader letters E, F, etc etc.
one of the reasons I now wait until all regular drives are connected and windows is installed and running, before I physically connect a card reader, they almost always take up the first available drive letters... have had one once, that took Drive C, and had to use H as my main drive, caused a lot of mayhem for some programs since they couldn't find Drive C, and wouldn't allow me to choose a drive, so couldn't get them installed.