Windows doesn't launch the application and all installed programs had .lnk extension
Delete the following key in your registry:
"HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.lnk\UserChoice"
You can do that manually with regedit, or copy and paste this line into your command prompt:
reg del "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.lnk\UserChoice" /f