Well, about 10 months ago I ran into the same problem. All good advises from here and several IT departments, professional shops, Microsoft and so on did only lead to the idea to re-install the Microcrap XP.
This was not a solution as I would have lost all and sundry on the harddrive. Tried to backup, re-install and use the backup on another (very same)machine, icon was still not there.
Solution was to get Pure Networks' Magic Network and I use this one to manage all wireless and plugged connections.... It is a work-around, but it was and is a very good solution in my case.
