@echo off
setlocal enabledelayedexpansion
set "ext=%~x1"
:loop
if defined ext set "ext=!ext:"=!"
if defined ext goto ok
echo 如果你不知道文件的擴展名，關閉批處理然後把文件拖到批處理文件的圖標上。
set /p "v=請輸入擴展名（如txt）然後回車："
for /f "delims=" %%i in (".!v!") do set "ext=%%~xi"
goto loop
:ok
echo 擴展名：!ext!
pause
reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\!ext!" /f
reg query "HKCR\!ext!" /ve|find /i "!ext:~1!_auto_file">nul
if not errorlevel 1 (
reg delete "HKCR\!ext!" /ve /f
reg delete "HKCR\!ext:~1!_auto_file" /f
)
taskkill /im explorer.exe /f
start %windir%\explorer.exe
pause

清除擴展名默認打開方式