So I'm looking to use a larger HDD for my Wii U. Basic stuff, right? This is all on legit 5.5.1 firmware—no CFW, nothing fancy. For the longest time, I've used a 2.5" 80 GB Toshiba HDD (previously from a MacBook) in a generic USB 2.0 enclosure, connected to the Wii U's back two USB ports via Y cable. This has worked just fine for a couple years now. I only have a few games installed to this 80 GB drive, but it's almost full. Regarding this Y cable—I use the same cable when I switch to vWii and connect to a different (but similar) 320 GB 2.5" drive for USB Loader GX, and I have no problems there. Note that if I were to try plugging in this vWii/FAT32 drive into the Wii U before switching to vWii mode, it prompts me to format the drive (as you would expect). I planned on following the basic guides out there for switching to a new, larger HDD. I have a 500 GB 2.5" HDD (from a PS4, actually), and it was previously FAT32 for some PC use. I wanted to copy data from the 80 GB drive to this 500 GB drive, so I knew I needed them both plugged in at the same time. To do so, I left the original drive in its USB enclosure and popped the 500 GB drive in a (powered) Voyager Q dock (see attached photos for comparison). Naturally, before doing so, I plugged in the 500 GB drive by itself (into the front USB port) and formatted the drive as usual. The process of copying files from the 80 GB drive to the 500 GB drive went off without a hitch. At this point, I can boot up the Wii U with just the 80 GB drive in its USB enclosure and see all my installed games as usual, and I can boot up the Wii U with just the 500 GB drive in its dock and see all my installed games just fine. However, when I switch them (as was my plan all along)—when I try booting up with the 500 GB drive in the USB enclosure connected via Y cable—nothing! The Wii U doesn't seem to see the drive at all! No installed games, no little USB icon, and no dice in system settings when looking at data management. However, the enclosure's green light is on, and I can hear faint activity on the drive (suggesting it's receiving enough power). If I unplug this 500 GB drive while the Wii U is on, it gives the normal warning message ("hey, only unplug drives when the Wii U is off"). Similarly, if I boot up with the original 80 GB drive in the powered dock by itself, I get the same results! No installed games, no USB icon, etc. If I boot up with both drives plugged in (as I successfully did when copying data between the two), it insists on going directly to the manage data menu (as one would expect), but neither of them show up! I'm flabbergasted. My only assumption is that somehow when the Wii U formats the drives, it somehow considers the drive and its connection/enclosure as one unit and can only recognize them in their original configurations. That being said, it's not like the Wii U bugs me to format the 500 GB drive when it's plugged in via the enclosure (as it does with my 320 GB vWii drive). When I swap them back (500 GB in dock, 80 GB in enclosure), they work again! Now, on my MacBook, either drive can show up in Disk Utility, but I can't exactly do much with them other than reformat them. Any ideas? Happy to try to troubleshoot/provide clarification.