When I actually take a second to consider what's really required for a fully functioning Wii U, that does all the stuff any core gamer would reasonably want it to do, it turns out this is actually a pretty bulky and clumsy console setup that takes up a lot more space and indeed plug sockets than I personally would like. It also makes it inaccessible to computers and other devices, so you'll need to dedicate a HDD entirely to the Wii U. You'll need to format it to use it with the Wii U, and that process erases any and all data on the drive. First though, if you're going to be using a USB drive you already owned, make sure you back-up everything you need off of it before you begin. Once you've got hold of your USB drive, it's a simple process connecting it to your Wii U. How do I hook up my USB drive to my Wii U? Our tests were performed on a 500GB Iomega HDD powered by Y-cable not listed on Nintendo's site, and we encountered no problems. Nintendo maintains a (currently very short) list of specific USB hard-disc drives known to be compatible with the Wii U at this link, though it's far from exhaustive - any drive that fits the basic specifications (external adaptor or Y-cable power supply, 2TB or less) should work. Note that USB thumb drives and flash storage are not recommended as external storage on the Wii U Nintendo has explained that because flash storage has a maximum number of reads/writes, it's unsuitable for the type of continuous data access needed to run games.