Rose, these sites have links to every type of psychological disorder. They are organized alphabetically.
Those are quite a variety of disorders for a powerpoint presentation. I would recommend just concentrating on one type of disorder, unless this runs against the requirements of your assignment.
You can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps a little more. Thanks for asking.