After the hints from Minkus (which he is correct from application point of view), I dig further and found out the root cause of the wrong icon is due
.ico file associated with other applications which were unable to handle the icon if the content of the
.ico file is actually a
.exe file, such as Windows 10 Photos app. In other words, when you double click on the
.ico file, the application which was launched was unable to handle the icon (due to what Minkus mentioned).
Instead of uninstalling the application which was associated with the
.ico file (which should work as well), just do the following:
- Find yourself an
.ico file, or just create one yourself by renaming a file to one with extension
- Right click on it, then choose Open with > Choose another app.
- Choose Paint, optionally check Always use this app to open .ico files, then click OK.
If you choose Always use this app to open .ico files, the icon should back to normal immediately. If you didn't, then you will need to reboot your PC.
This should fix most wrong icons on taskbar, desktop, shortcut, except those in Start Menu search result which I still have no idea how that can be fixed.