At once I cant use Windows Photo Viewer as standard app for jpg extensions, Windows doesn't show the jpg extension Same problem with VLC media Player,as standard app for avi and mkv-i extension I guess it was after installing an update but which one?
This is a registry corruption, ie, .jpg, jpeg is missing from the HKEY_CLASSES_ROOT registry for file extensions You have simply deleted them from there by some method and it has nothing to do with any updates. To fix it, you just need to add them there again and set the default program to the program that suits you. But it's worth remembering that it may not be the only one you've removed from the registry. It would be reasonable to restore the original registry of Windows and the matter is OK. I would also recommend checking and, if necessary, restoring all default file extensions and associations. The simplest way is to use registry backup file. If You don't have any of them, make it on some other pc and restore default registry. If done, reset default programs for any or all or selected file type and You're done. I remind you that, that Yamicsoft Windows Manager RepairCenter helps restore all default file associations with one click. Also the registry manager helps backup and restore whole default registry with one click. I hope, You know that.