Under the Timing tab, select Animate automatically after 0 seconds, Under
the Effects tab, select Appear, and Under the Play Settings tab, under Object
Actions, select Activate Contents, then click the OK button.
Next cover up the pink icon on the slide with a square box (ideally the
same color as the background) - I like to use a solid black background for
this slide and cover up the pink Flash icon with a solid black box.
Next, under the Slide Show menu, select Slide Transition, Set the slide to
transition Automatically after 0 seconds using whatever transition effect you
want.
Next, go to Options (typically under the Tools menu) and set the virus
protection to LOW (under PowerPoint 2000) or deselect it (under PowerPoint 97).
Finally, go to Slide Show mode and watch your Flash movie play full
screen, then transition after playing directly to the next slide in your
presentation.