I plugged it in and I could see the files, but they would not play. It would just boot me back to my last source, in my case my PC. Over and over again I tried every solution I could find. For days I scoured forums to no avail. I called Samsung and spent 40 minutes on hold, being transferred to various departments with nary a solution in sight. I considered returning it, but then decided a TB drive for fifty bucks wasn't a bad deal.I started loading it up with other 4K files, but itching in the back of my brain was all these great files that were right there, but I couldn't view. Since my other 4K files worked fine, I started wondering if I could just change the .um4 extensions because the TV clearly wasn't understanding them and I highly doubted Samsung created a completely different codec for these files.So as a last resort I tried a very simple experiment. I loaded a .um4 file into Super video converter. Low and behold, it showed me that it was in fact an mp4 file. Could it be that simple? Could I really just change the stupid extension from .um4 to .mp4 and it would work?YES!!!!! IT WORKS! Formally completely unrecognized files, now all work perfectly with .mp4 extensions! It's just so ridiculous! Why hasn't anyone figured this out before me?Anyway, hopefully I have helped someone out and you can breath a sigh of relief that yes, the files do work. I don't know what Samsung was thinking sending these files out when most of the TVs seemingly don't understand them, even with the latest firmware.As for the files themselves, the documentary stuff is breathtaking. SOME of the movies look good, like Star Trek Into Darkness and Wolverine, but some don't. Forrest Gump for example looks worse than Blu-ray. The first Star Trek and WWZ don't look that great either. Life of Pi is so-so. I'm basing this just on the first few minutes though so they may get better.Thank you Samsung! I am more addicted to my new 4K TV now that you released a new UHD Video Pack with 10 movies and at least 20 or 30 documentaries in glorious 4K!! The movies are what this device is ALL about! The documentaries (only about six are worth watching) are mainly snippets (2 to 4 minutes long) and most are not interesting (puppies playing!?) but a few are. Its all about taste and everyone is different. This new device has the same movies on it as the first one (The Counselor, World War Z, Wolverine, Night at the Museum, GI Joe) and Samsung added Forrest Gump, Life of Pi, The Book Thief, Star Trek (2009), and Star Trek Into Darkness. The two films that benefit the most in 4K are the Star Trek movies. OMG, I have never seen that much detail on the blu rays (even the 3D versions) as I see on this UHD Video Pack! What an amazing experience. These newer films really benefit from this 4K device. Forrest Gump has never looked as good as it does here (hard to believe this film is twenty years old) and opened up the colors and detail like never before! I am sure Life of Pi looks amazing, too (I have not had the chance to check it out yet) but I just wanted to spread the word on this newest device from Samsung. I was fortunate to get this for under three hundred bucks, but if you can spare the extra cash, go for it! You can always sell your first one on Amazon (I sold my pretty quick) to help with the hefty price tag. This knocks the first one out of the ballpark! Still waiting to hear from Samsung if they are able to download more content onto this device without having to plop down several hundred dollars for another one (at this rate Samsung will put us 4K addicts into the poor house). For the time being, I am glad I have great looking 4K to show off my TV!For anybody that owns a Samsung 4K TV and is wondering whether or not to purchase this accessory, wonder no more! This nifty little unit is easy as can be to plug and play with ZERO problems at all. Just make sure to plug the unit into the HDD USB jack and select "UHD Video Pack" as your source on the SmartHub. It really is that simple. Contrary to what I read in other reviews here, the content is absolutely 100% 4K UHD; NOT simply an upscaling. We have a 2016 70" Samsung 4K UHD TV (UN70KU6300), and for those that complained about the quality (UHD-vs-DVD; etc.,) my guess is that they did not plug their unit into the HDD USB jack. If they had, it is crystal-clear that every title pre-loaded onto this external storage unit is, indeed, UHD.Others have mentioned that they would never pay for this accessory since it was given away with purchase for select Samsung 4K UHD televisions in the past. While that might very well be the case, that would have been in 2014, when the price of a 4K UHD television was a whole lot more than it is now! Given the choice, I would rather pay what I paid for our TV in 2016 along with the $38 paid for this UHD Video Pack any day given the difference in price and technology then and now. On that note, the instruction manual included with the unit states that it is only compatible with 2014 Samsung UHD TVs, that is obviously not the case. It works just fine for us.Given not only the capability for additional UHD storage, but the titles and the quality of the titles included with this unit, I would recommend this UHD Video Pack to anyone that owns a Samsung UHD television. We are more than happy with this purchase, and I hope this helps anyone thinking about nabbing one of these while they're still readily available.Great experience - I reached out to the seller to ask more questions and received a response within the hour. As for the item it arrived ahead of schedule and has been s great addition to my uhd tvQuite a few movies and documentaries. Arrived quickly. No issues.Just an Awesome addition to my 65in Curved TV !