I am reopening this very old, unresolved thread because I have run into the same issues with a refurbed dc7900 purchased from TigerDirect. I am NOT a SysAdmin. I have updated the BIOS as per the thread. I have tried unsuccessfully to update the ME firmware using both the DOS method and the Windows method. Both methods give error messages, but different ones. In DOS the error message states it can't open the BIN file as it's already open. In the Windows method I get the message the ME driver can't locate the proper ME device.
I have gone into Device Manager. It indicates that Intel Active Management for COM 3 has been suspended due to problem with the device. Currently it uses Intel AMT driver vers. 5.5.1.1012 date from 2009. I would disable this device except I have no idea what it is.