Been there, done that.
One way to fix that is to go into the folder options, file types and delete the boo boo.
Then open an icon file and choose the correct program and make sure the checkbox is checked to open all.
Another method might be to reinstall Icon packager but that way I don't know for sure.
Little tip: You can open most everything with notepad but make sure the open all checkbox is not checked when doing so.
