Windows 8.1 內建的 Windows Defender 提供即時防護，但部分使用者發現無法開啟且提示檔案損毀。此問題多半源於登錄檔鍵值錯誤，可透過系統檔案檢查器與登錄檔修復指令解決。

修復步驟

1. 以系統管理員身分開啟命令提示字元：按 Win+X 選擇「命令提示字元 (系統管理員)」。
2. 執行系統檔案掃描：輸入 sfc /scannow 並按 Enter，靜待掃描完成（過程可能卡住數分鐘，請耐心等待）。
3. 匯入修正登錄檔：掃描完成後，將下列完整指令複製貼上至命令提示字元並執行（指令較長，請確保完整貼上）：

   reg export "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend" %Public%\Desktop\Reg_WD備份.reg & echo Windows Registry Editor Version 5.00 > %temp%\Reg_WD.reg & echo. >> %temp%\Reg_WD.reg & echo [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend] >> %temp%\Reg_WD.reg & echo "DisplayName"="@%ProgramFiles%\Windows Defender\MpAsDesc.dll,-310" >> %temp%\Reg_WD.reg & echo "ErrorControl"=dword:00000001 >> %temp%\Reg_WD.reg & echo "ImagePath"=hex(2):22,00,25,00,50,00,72,00,6f,00,67,00,72,00,61,00,6d,00,46,00,69,00,6c,00,65,00,73,00,25,00,5c,00,57,00,69,00,6e,00,64,00,6f,00,77,00,73,00,20,00,44,00,65,00,66,00,65,00,6e,00,64,00,65,00,72,00,5c,00,4d,00,73,00,4d,00,70,00,45,00,6e,00,67,00,2e,00,65,00,78,00,65,00,22,00,00,00 >> %temp%\Reg_WD.reg & echo "Start"=dword:00000002 >> %temp%\Reg_WD.reg & echo "Type"=dword:00000010 >> %temp%\Reg_WD.reg & echo "Description"="@%ProgramFiles%\Windows Defender\MpAsDesc.dll,-240" >> %temp%\Reg_WD.reg & echo "DependOnService"=hex(7):52,00,70,00,63,00,53,00,73,00,00,00,00,00 >> %temp%\Reg_WD.reg & echo "ObjectName"="LocalSystem" >> %temp%\Reg_WD.reg & echo "ServiceSidType"=dword:00000001 >> %temp%\Reg_WD.reg & echo "RequiredPrivileges"=hex(7):53,00,65,00,4c,00,6f,00,61,00,64,00,44,00,72,00,69,00,76,00,65,00,72,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,49,00,6d,00,70,00,65,00,72,00,73,00,6f,00,6e,00,61,00,74,00,65,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,42,00,61,00,63,00,6b,00,75,00,70,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,52,00,65,00,73,00,74,00,6f,00,72,00,65,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,44,00,65,00,62,00,75,00,67,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,43,00,68,00,61,00,6e,00,67,00,65,00,4e,00,6f,00,74,00,69,00,66,00,79,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,53,00,65,00,63,00,75,00,72,00,69,00,74,00,79,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,53,00,68,00,75,00,74,00,64,00,6f,00,77,00,6e,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,49,00,6e,00,63,00,72,00,65,00,61,00,73,00,65,00,51,00,75,00,6f,00,74,00,61,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,41,00,73,00,73,00,69,00,67,00,6e,00,50,00,72,00,69,00,6d,00,61,00,72,00,79,00,54,00,6f,00,6b,00,65,00,6e,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,54,00,63,00,62,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,53,00,79,00,73,00,74,00,65,00,6d,00,45,00,6e,00,76,00,69,00,72,00,6f,00,6e,00,6d,00,65,00,6e,00,74,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,00,00 >> %temp%\Reg_WD.reg & echo "FailureActions"=hex:80,51,01,00,00,00,00,00,01,00,00,00,03,00,00,00,14,00,00,00,01,00,00,00,64,00,00,00,03,00,00,00,64,00,00,00,00,00,00,00,64,00,00,00 >> %temp%\Reg_WD.reg & echo "LaunchProtected"=dword:00000003 >> %temp%\Reg_WD.reg & echo "FailureCommand"="C:\WINDOWS\system32\mrt.exe /EHB /ServiceFailure "CAMP=4.6.305.0;approximate- Engine=1.1.11202.0;AVSIG=1.189.1057.0;ASSIG=1.189.1057.0" /q" >> %temp%\Reg_WD.reg & echo. >> %temp%\Reg_WD.reg & echo [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend\Security] >> %temp%\Reg_WD.reg & echo "Security"=hex:01,00,14,80,f4,00,00,00,00,01,00,00,14,00,00,00,30,00,00,00,02,00,1c,00,01,00,00,00,02,80,14,00,ff,01,0f,00,01,01,00,00,00,00,00,01,00,00,00,00,02,00,c4,00,07,00,00,00,00,00,18,00,9d,01,02,00,01,02,00,00,00,00,00,05,20,00,00,00,21,02,00,00,00,00,14,00,9d,01,02,00,01,01,00,00,00,00,00,05,12,00,00,00,00,00,18,00,9d,01,02,00,01,02,00,00,00,00,00,05,20,00,00,00,20,02,00,00,00,00,14,00,9d,01,02,00,01,01,00,00,00,00,00,05,04,00,00,00,00,00,14,00,9d,01,02,00,01,01,00,00,00,00,00,05,06,00,00,00,00,00,28,00,ff,01,0f,00,01,06,00,00,00,00,00,05,50,00,00,00,b5,89,fb,38,19,84,c2,cb,5c,6c,23,6d,57,00,77,6e,c0,02,64,87,00,00,28,00,ff,01,0f,00,01,06,00,00,00,00,00,05,50,00,00,00,bf,55,08,72,3b,e0,28,d0,89,79,4b,f8,91,89,6e,7c,40,25,ec,f4,01,01,00,00,00,00,00,05,12,00,00,00,01,01,00,00,00,00,00,05,12,00,00,00 >> %temp%\Reg_WD.reg & reg import %temp%\Reg_WD.reg

4. 啟用服務：執行完成後，開啟「服務」 (services.msc) 找到 Windows Defender 服務並啟動。

小提醒：此操作會在桌面產生 Reg_WD備份.reg 備份檔，未來若再發生同樣問題，雙擊該檔案即可快速修復。