@echo off

set local

if {%1}=={}goto syntax

set ext=%1

set ext=%ext:"=%

set wrk=%ext:.=%

if "%wrk%" EQU "%ext%" goto syntax

for /f "Tokens=2 Delims==" %%i in ('assoc %ext') do call :reg %%i

endlocal

goto: EOF

:syntax

@echo Syntax: NeverShowExt .ext

endlocal

goto :EOF

:reg

if "%wrk%" EQU "%ext%" goto syntax

@echo Windows Registry Editor Version 5.00>%TEMP%\NevershowExt.reg

@echo "NeverShowExt"="">>%TEMP%\NevershowExt.reg

regedit /s %TEMP%\NevershowExt.reg