"Some of my iPhone 5 videos play sideways on my computer (Window 8). Is there any easy way to rotate the videos so it plays correctly?"
The reason your iPhone videos playback sideways on computer is that you held the iPhone vertically when you recorded the video. If you hold your iPhone vertically, the way you talk on the phone, the recorded video will in 9×16 aspect ratio and plays sideways on the computer or HDTV screens, which expect your video to be 16×9 aspect ratio. Videos recorded in landscape mode could be upside down if the home button is on the left hand side. There is an easy way to fix this problem, with the help of some third-party software to make it work. The steps that follow will help you rotate iPhone video to make it play correctly on your computer or big screen TV.
For Mac users, you can rotate your videos from iPhone by using the iSkysoft Video Editor for Mac. For Windows users, although Windows Movie Maker supports video rotation, but bad news is that iPhone video are in a format that Windows Movie Maker can't recognize. So, iSkysoft Video Editor for Windows will help you do the task.
Guide to Rotate iPhone Video using iSkysoft Video Editor
For this tutorial, I show you how to use iSkysoft Video Editor to rotate and edit your iPhone video. Once you have the program installed, the steps to rotate your iPhone video are plain and simple.