I want to create animated gif of photos, like the screensaver of macs ?
Which program will do it as default ? I am using windows.
I want to use it in power point.
To answer both your questions and Cai's question, you CAN actually do this directly in PowerPoint by adding the photos as slide backgrounds and using slide transitions.
It's literally the best approach not only because a GIF doesn't get along with photos but you can actually go back and edit your images/transitions/styles/time and so on.
So, basically, it's easier, faster, at a better quality and you have more control over it.