I excidently downloaded fwbackdoor.txt into my system, my antivirus (norton, pc cillin nor trojan scanner) can't find the virus!

How would i go about to take this fwbackdoor.txt out of my system?

backdoor downloaded from the (backdoor and rootkits category) here in -antionline.com-! PLEASE HELP! and YES u can call me DUMB Thank YOU please help!