portable edition became default browser but not supposed to

Portable edition of Ice Dragon suddenly became the default browser while doing a computer use internet session. Not supposed to happen, according to information in Options for portable Ice Dragon. When I closed it, and then opened Internet Explorer version 9, I chose to make IE the default, and in doing so, the shortuct for Ice Dragon disappeared.

(I setup a new desktop shortcut for Comodo Ice Dragon; and so far, IE continues to stay as the expected default browser).

This done and seen in Windows Vista, 32-bit, on laptop computer.