Hello @dstuebgen ,
I feel your pain... .avi files are not the most convenient of video formats. And some Windows 10 video softwares do not natively reproduce them. You would need to convert to .mp4 or another common format to visualize them.
However, you probably already have installed Windows Media Player (I think it comes with any Windows). If you do, click the right button on the .avi file, and select 'Open with' -> Windows Media Player. It should work as it has .avi compatibility.
To create animations in nonlinear simulations, I usually right-click Results -> Multiset Animation Settings. A window will pop-up where you can select the properties you want. There you can set which step to start and end (usually I start at step 1 and end at the last step) and the step increment (1 to 1, 10 to 10, etc); in the Animation Options tab you can select full (start -> end -> start) or half (start -> end) mode and the time delay between frames. Then you can click 'Animate' to preview or 'Create AVI' to generate the video file.
The time to generate the video will depend on your machine and the size of your model (a higher number of elements/nodes will take longer to process each step), but you can tweak those multiset animation settings to only show certain steps (as changing the step increment to 5 or 10 or 20, etc). For instance, in this example below I have 274 steps and set 'Increment' to 5, so the animation will only take the 1, 6, 11, 16, 21, ... steps and take less time to be created than if 'Increment' was 1:
