missing dvd rom in windows 8

i Try this. Open a CMD prompt with admin rights and run this: 

Reg.exe add "HKLM\System\CurrentControlSet\Services\atapi\Controller0"/f /v EnumDevice1/t REG_DWORD /d 0x00000001

 AND access denied and my dvd room still missing 

please HELP ME my dvd room is pionner DVR-218L