Pop-up and other adds.when I boot my computer

Hi, I need help getting rid of annoying pop-ups that appear every time I restart my computer.  I have gone through my files and can't find this thing listed.  I have deleted other registry cleaner adds but they seem to be able to worm their way back on.  The one I have sitting on my computer right now is http://update.downloadhelper.net/index493.html

I thought N prevented pop-ups.  We have been customers for 4 years and this is a new problem. What can I do to get rid of these annoying pop-ups. karenrita