This problem usually happens on Windows 8 after doing a system restore.
The solution is to just create a new account if it’s still broken then you must repair it manually :
- Clear the icon cache
- Use FileTypesMan or the default Windows association tools in control panel to reassociate files easier
p.s I forgot the name, but in Windows 8, there’s a menu in control panel so that you can see which extensions are supported by each programs so you can just tick in every extensions that you want to be associated with those programs.