Trojan.Zeroaccess, Trojan.Gen.2 and Trojan.Agent infecting my computer

Yesterday my PC got infected with Trojan.Zeroaccess and Trojan.Gen.2.  Symantec Antivirus auotprotect reported a swarm of Trojan.Zeroaccess and Trojan.Gen.2 infections.  After multiple scans SAV no longer reports that the viruses are on my computer.  However real time protection is disabled and I cannot restart it.  Similarly Windows Firewall is disabled and cannot be enabled.

 

Malwarebytes reports that Trojan.Agent is infecting my computer as well.  I don't know if this is related to my Zeroaccess and Gen.2 infection.  Any help would be appreciated.

 

My PC is running Windows XP SP3 and I have a flash drive.