The first thing to try would be to reinstall Fritzing to make sure the code isn’t corrupted. If that doesn’t fix it try clearing the user directories (which don’t get modified during an install) although that doesn’t usually affect file saving.
There are two user directories (with your parts and the parts database) which don’t get touched during an install (to not affect your sketches during upgrades). On Windows they are in
c:\users\username\AppData\Fritzing\roaming\Fritzing (which is a hidden directory so you need to enable hidden directories in explorer) and
c:\Users\username\My Documents\Fritzing (where username is your windows id)
If you don’t have any parts or sketches you want to keep you can just delete those two directories and Fritzing will recreate them, or you can move them aside by renaming them if you want to keep something in them.
OK, then try enabling the debug log in Help->Enable debug log, then create save a sketch with a single resistor in it like this, at this point I have only dragged the resistor in to the sketch.
Well that is disappointing! All looks normal as far as it goes, but no indication of what file it is attempting to write (it should be Untitled sketch.fz though, but it may be a temp file that isn’t showing in the debug log as well.) You will need to enable Show hidden files, folders and drives in the explorer folder options->view window to be able to see app data, then display the fzz directory like this:
I’m going to guess the .fz file won’t appear but we don’t know why it doesn’t on your system. At this point I don’t know what else can be done. The only thing I know will work is to install a development environment and debug (although I normally debug on Linux with gdb because I have never been able to figure out how to use the Windows debugger!) but that isn’t a small undertaking. Maybe someone else will have a suggestion that I haven’t thought of though. It may be worthwhile to make sure you can write a file in to the directory in app data that gets created as this may be a permissions problem of some kind that is blocking the write from completing.
That is bad, but the fact that it runs on a second Win10 system indicates it is something about that one Win10 system. The second Win10 system is the usual case, it usually just works.
A late thought on something to try, this is usually done because something is corrupted, but in this case it may clear the problem because Fritzing should recreate the directories with the permissions it wants. You should be able to just delete both directories as there shouldn’t be anything in them that you want. Make sure they get deleted, because the permissions may be the problem. Worth a try anyway.
There are two user directories (with your parts and the parts database) which don’t get touched during an install (to not affect your sketches during upgrades). On Windows they are in
c:\users\username\AppData\Fritzing\roaming\Fritzing (which is a hidden directory so you need to enable hidden directories in explorer) and
c:\Users\username\My Documents\Fritzing (where username is your windows id)
If you don’t have any parts or sketches you want to keep you can just delete those two directories and Fritzing will recreate them, or you can move them aside by renaming them if you want to keep something in them.