OBS is free and easy to use
https://obsproject.com/download
add source
window
select window (in my case ras mapper)
click start record
you may need to change the video driver, i had to switch to hardware(qsv) under settings-output
in this menu I also changed the output to mp4 to reduce size. if the video fails for any reason throughout the process with mp4 you will lose it all, but i am making short videos not streaming for 2 hours.