  back up your data ... format your hard drive ... do a complete new installation of windows 7 ... no matter what all the experts say about removal starting from scratch is the best way to be sure ... the fact that McAfee can't get them off of there means it's pretty clever trojan.    Reinstalling Windows and rewriting the MBR is enough. The hard drive doesn't have to be formatted. It may also help to run an offline AV scanner from removable media, as that will disable rootkit-type defenses.  
I have a Dell Inspron 620 approx 13 months old, running McAfee anti virus software. I have 2 trojan viruses which are causing problems, one of which is to continually disable the firewall. McAfee is detecting them but is unable to delete them. I would appreciate any suggestions on the best way forward to deal with them. I have looked on the net and one suggestion was to run a complete scan in safe mode, which I have done. This did not detect the viruses so did not achieve anything. I was wondering if setting the computer back to factory setting, as it was shipped to me may be the answer, but am not sure if it will detect the trojans. I am running Windows 7. The viruses are identified as : RDN/Generic BackDoor!sl
Trojan Virus Removal