Hide|Show extensions for known file types from cmd
Open command line window and execute:
Hide extensions
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced /v HideFileExt /t REG_DWORD /d 1 /f |
Show Extensions
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced /v HideFileExt /t REG_DWORD /d 0 /f |