You will find that these AV things burrow themselves deeply in the registry and the start-up sequences. To begin with, hit ALT-CTRL-DEL and see whether you can see the AV program running there; if it does, kill it. Then, in regedit, search for all instances with the name of nod32 and delete them all, left and right window; that can be a lot of entries. As last run msconfig, check everything there for that *$@# ! and untick them . Then re-boot and, as it will not be running any more if you did that before well, you can erase its folder in \Prgram Files.
Davec's unlocker: you say "Yeah I also have tried that. It's the problem when I try to close it,..." This should not ask for closing something; check the way-of-proceeding on that page. Find the program folder, right-click, if necessary kill the process, unlock it and then erase the whole thing. Run msconfig and regedit and reboot.