In Auto Movie Creator, you can select all the photos, then add them to the Storyboard with a single drag-and-drop.

Then, to add a transition between each photo, just click anywhere in the Storyboard, and press Ctrl-A to select all the clips. Now, click on the Transitions button to open the Transitions Collection, right-click on any Transition, and choose Add To Storyboard. The selected Transition will be added between every clip on the Storyboard.

A 50-slide show could be completed in seconds.

You can set the duration of both the bitmap images and the transitions by clicking the Tools menu, and selecting Options. The first tab of the Options window lets you set the duration for both Image Sources and Transitions.