Hello, let me present you a very basic and informative piece of information between concepts of Detected and Undetected drives.
Detected Drive: A drive that is recognized by your computer at its full capacity and allows access to user area is called as a detected drive. Detected Drive but no access to User Data, this is altogether a different kind of a problem where the drive is detected but fails to read any data. WD drives usually experience this. Other drives such as TOSHIBA USB3 are reported with such problems. Drives can at times show up in system but fail to give any data due to problems like encryption or at times they are just sharing their identity from the PCB itself and not from its Service Area.
Undetected Drives are the drives which do not get detected in the computer. They come with various other faults at times like clicking, spinning down in a few seconds or not spinning at all.
This can be easily viewed on our services page as a block diagram.