hey i was tricked into downloading a file to play a video on youtube

i now have trojan.zlob, i keep getting pop ups directing me to download antivirus software. More annoyingly, on my task bar i constantly get an alert directing me to one of these websites.

i was using norton internet security but that was unable to detect and deal with this trojan. so i uninstalled it and downloaded the latest version of sophos. i ran this but it did not detect the trojan.zlob. Instead it cleaned trojan-avv(something like that).

I am still having the same problems. I am using vista. I dont know how to get rid of it