Press your windows key on the keyboard and search
xbox. Open the xbox application and go through the initial setup if you haven't opened it before, takes less than 5 minutes. Then once in the main app click the
SETTINGS gear. At the top it says General / Game DVR / Xbox One / Network / etc. Click on
Game DVR and turn off
Record game clips and screenshots using Game DVR
This is the windows key:
This is how the setting should look like:
If you also see an option
Show Game bar when I play full screen games Microsoft has verified, uncheck it