When KiCad software is uninstalled, it leaves behind files inside the registry (as almost all applications do).
For KiCad, this created a problem (at least on my windows). I had KiCad 8.x, uninstalled it and installed KiCad 9.x and windows would still try to open my .kicad project/pcb/sch files with KiCad 8.x, instead of switching to 9.x. I could not fix this via the default apps settings, windows would still look for KiCad 8.x
I tried many different stuff in Windows. What eventually made windows understand there is no more KiCad 8.x, was to look for the “KiCad” keyword in the registry and delete all the occurrences of KiCad 8.0 (I also removed KiCad 9.0 occurrences) and installed KiCad 9.x again. Screenshot from some Register entries:
This issue is caused when switching from major version (8.0 to 9.0 for example), because the installation directory of the .exe files changes.
I would like to see a option to delete these registries via KiCad install or uninstall procedure, maybe with a warning.