AVI frame to still image?  

I use a free Open Source command line utility called FFmpeg https://www.ffmpeg.org/ for most of my video processing and editing.

One of its options is to convert a video into a sequence of individual images (it can also do the reverse, turn a sequence of images into a video). To extract half a second's worth of .png images from an AVI video starting at 5 minutes in, the command line would be:

ffmpeg -i input.avi -ss 300 -to 300.5 image%d.png

The %d is replace by a number, for a 25fps video this command will produce images named image1.png to image12.png

Note that if the video is widescreen (16:9) you may find the aspect ratio of the extracted needs adjusting because the pixels in the original video are not 'square' (they get stretched by the codec when you watch the video). FFmpeg has a 'scale' video filter (-vf) that can adjust for that. You may need to work out from the size of the video frame and the aspect ratio exactly what figures to use. As an example:

ffmpeg -i input.avi -ss 300 -to 300.5 -vf scale=1280:720 image%d.png

Working from a command line is fiddly, but FFmpeg is very powerful, so I find it's worth the effort.

Most decent media players can save stills or screenshots.

PotPlayer

LightAlloy

Shotcut (video editor)

If you use WMP then I think you're stuck with snipping tool or PrintScreen options.