I\'ve noticed, that some USB storage devices don\'t register in Windows as regular drives, in that they don\'t even get assigned a drive letter. Therefore, I can\'t apparently a
If you're talking about mobile devices that appears like mounted volumes but without any mounted points, well they are called Windows Portable Devices and they are not mounted volumes.
Windows doesn't access the file system directly, it only communicates with them through the Media Transfer Protocol (MTP) or Picture Transfert Protocol (PTP) and creates a shell namespace extension to present a virtual folder to the user.
If you want to communicate with these kind of devices, then you most probably want to use the WPD API.