x box 360 disc drive firmware?

 On july 2008 i bought my 4th x-box 360 and this time i got a halo limited edition thinking it would maybe perform better but the same problem came back,it does not want to read any type of discs. In early september i bought an X-BOX 360 DVD DRIVE,HITACHI LG 79FK GDR-3120L  NEW! (Other) (79fk). I replaced the old one and apparently,i need a firmware. Would someone explain me what it is or what i need to do. Thanks to all. any tips would be very appreciated