Bing is very sticky, it is an add on, not a program installed in your computer like others.
For remove bing from ie8, go to tools/ add ons and remove Bing.
If you are using firefox, Bing keeps or hack-crakcs your seetings from

ie8, you must unistall the bing from Internet explorer first, then unistall it from firefox, once you remove the add-on, still will be sticky in your "searches", the solution is unistall firefox and then install it again.
Before install firefox again, make sure is removed from internet explorer, otherwise, bing will try to hack -crack in your firefox instalation again.
For make sure bing has been removed, open ie8 and search something, if the search is from the bing home page, then still you have bing in your system, do not install firefox until you remove it from ie8.
I did it and is the only solution!!!!!