I searched online to find info on how to rotate my MP4 videos. There are several Microsoft Community web pages on this question that say that it isn't possible, mentioning applications that Microsoft no longer supports & other problems. I tried to submit a helpful answer on one of these questions, but the thread has been locked. Why don't you admins go back to these Community threads on this problem and add a useful answer? I've also found misleading answers on Microsoft Support pages. (I selected Windows Media Player as the product, but there are questions about this issue on forums devoted to other products, such as Photos, as well.)