I prefer NanoVNA app by OneOfEleven instead of NanoVNA Saver. It has better graphing capability and it is easier to scale plots. A forked version with some bug fixes by Owen Duffy is available at the link below. It works on WIN7
I wrote a post on how to navigate the menus. Lots of getting started info...
/g/nanovna-users/topic/91143866#28096Roger