You can use the GetLogicalDrives API to get all drives. Then use the GetDriveType API with one of the following flags
DRIVE_UNKNOWN The drive type cannot be determined.
DRIVE_NO_ROOT_DIR The root directory does not exist.
DRIVE_REMOVABLE The disk can be removed from the drive.
DRIVE_FIXED The disk cannot be removed from the drive.
DRIVE_REMOTE The drive is a remote (network) drive.
DRIVE_CDROM The drive is a CD-ROM drive.
DRIVE_RAMDISK The drive is a RAM disk.

to see which drive is a CD_ROM.