Can't login to computer. can't get out of Safe Mode back to Normal

I am having Symantec Antivirus installed in my system running on windows 7 64 bit. Early this morning when i carried out a scan, it reported me some Trojan horse along with instruction to deal with it. It was to first boot in to safe mode, i did the same but after booting in safe mode when i entered username and password i got an error. Current situation is that i am not able to login and i am not even able to get out of Safe Mode as hitting F8 on start up is doing nothing. I am totally lost, is there anyone who can help me out in this situation???

See if you are having your windows 7 64 bit installation disk than you can boot from it and carry out a Repair. It wont deal with Trojan but will let you get out of safe mode and enter Normal mode. Since your Symantec Antivirus is not appearing to deal with Trojan i will suggest you to uninstall it and install Avast. I have used avast for couple of months and it is quite capable of dealing with all kind of viruses,malware,trojan etc.