When you export your slideshow to WMV in Premiere Elements 3.0.2, you can make your images look better if you go into Advanced Settings and change the Keyframe Interval to match the length of each still on the timeline. By default stills have a length of 5 seconds, and so does the Keyframe Interval for WMV. Coincidence?
If you create a slideshow where the length of each still is 10 seconds, then change the Keyframe Interval to 10 seconds. If the stills vary in length, then change the Keyframe Interval to 100 seconds. If the keyframe interval is set to 1 second, you will see "burps" every second unless your stills are also 1 second.
For a DV-AVI that I have, using a Keyframe Interval of 100 seconds produced the best WMV.
You can also make your images match the quality that Windows Movie Maker produces by using the Sharpen Effect on stills and video. Use a value of 16.
That's the significant part of what I posted over on the Adobe Premiere Elements Forum. Someone was asking for help with exporting to WMV.