I downloaded and tried out that ICO plugin, and it gives me no problems. I can't explain your problem with the help.html file repeatedly popping up - I've got CS2 and that file doesn't exist in my installation - but maybe it's another symptom of your "dodgy" computer, as you mentioned in a previous thread?
As to icon size, this might be helpful:
http://msdn.microsoft.com/library/de...winxpicons.asp