I believe it is part of Dell's quickset feature.  You may have disabled it, or uninstalled it.. or changed some settings in it..

If nothing else, just download it and reinstall it, that should make it work again ;)

edit* reading through your other posts, it sounds like you have some major computer problems.. you may just want to do a factory restore from the recovery partition, or just reinstall XP all together

Good Luck!!