How do i change the size of my messenger conversation box, now it takes up the whole screen,?

i used to have a normal sized messenger box, now it takes up my whole screen it never did that before, i never changed anything, when i updated yahoo to the latest it changed my screen and it is quite annoying, how do i get it back to normal????? any help would be appreciated.How do i change the size of my messenger conversation box, now it takes up the whole screen,?
First click the picture of the Double Boxes between the X and the Minimize buttons in the upper right hand corner... Then if you hover over the lower right hand corner a diagonal symbol with arrows on each end will appear.. Once it appears click and do not release and just pull it in the direction you want the screen to shrink! It will stay that size the next time you open Yahoo also! :)