How do i dn load a later version of explorer? i have 7 but now i can't chat it cuts the box off at the bottom

when im on pogo playing i cant chat it cuts the box off and im pissed how do i get rid of explorer 7 and get a earlier version or a differt one? please help. also the reason is the border is to thick does anyone know if i can change it need help please!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!