Yesterday I start receiving Norton warnings from the autoprotect, in regards to Trojan.Gen.2, trojan horse and downloader. The message indicated that autoprotect blocked those threats. However I notice that the windows firewall and the MS antimalware tool were not working. Now I can't launch any of those. And when I try to run a symantec scan I receive an error (Norton error 0x00003f4) and the scan does not start. Apparently also my antivirus is not working. Another symptom was that when I rebooted my PC yesterday, it could not start normally and start searching for repair. I have Windows Vista 32 and Symantec Norton Internet Security. How can I clean my system? Thanks.