Task is assigned on .qvw files. so what happen with you is that you assign reload task on .qvw file. so qlikview make image for that task and then you directly delete that .qvw file from the location on which you assign reload task. So you delete from source location but on qmc it's image always be there because u didn't disable the Task.
So Step 1:
Come to source location where you delete .qvw file and make .qvw file with exactly same name.
after creating come to qmc then you see that qvw file is exist in Documents tab and on that .qvw file reload task is assign so first you have to disable that task and press apply.
Make sure you didn't apply license on that if you apply license on that so delete the license from that file as well.