PLZ help me guys with my nokia phones ....?

Hi i have a nokia c5-03 .. i bought t about 2 weeks ago ... now just like any other s60v5 phone when i press options button a green circle appears beside show open apps .. lately i installed a number ( about 10 ) themes and i dont remember after applying which theme the green circle vanished and instead a white square appeared .. can anyone tell me what i should do to get the green circle back ... also does anyone know how to format a nokia 2600 classic .. it is an s40 phone .. thnx in advance ..