I always missed the "view image in full screen" mode in my Vista installation, because out of the box it does not work with my Intel 950 video chip - when I clicked the Slide Show button it switched video mode back to something below 1024x768 (I'm using a 19" LCD with 1440x900 resolution), and created a horrible performance and huge artifacts while switching pictures.
After some goggling, I've found the Microsoft KB article id #930102, dealing with "choppy image transition" quality. At the end of the article, you can find the solution: hack the registry, and set the WinSATScore to 500, to use the native video resolution. The transitions will be painstakingly slow, but you can press the Pause button to stop it, BUT going back and forth manually does not include transitions! :)