Ok, after rocking a .png file as a desktop wallpaper for a few days, I've discovered something. Namely, do NOT use .png files as desktop wallpapers. At least not in Windows XP Pro. Even though Windows gives you the ability to set .png's as wallpapers, it seems to wreak havoc with the video memory. I am re-uploading my two Betty Boop wallpapers as .gif's. I would have preferred something that doesn't lose as much color information, but it looks decent enough. And, importantly, it doesn't have Jpeg's awful compression blocking.
Betty Boop Wallpaper 2 16:10 ratio:
Betty Boop Wallpaper 2 4:3 ratio: