I don't know why, but after using the "WinXP Tweaking: From Reformat to Relax" guide, my wallpaper is now offset on my desktop. I have about 1.5" of space showing on the top and left sides of my wallpaper when I set it to stretch the background. With it set to center, it doesn't show in the center, it's offset down and to the right. It does this no matter what resolution the display is set to, from 800X600 to 1280X1024.

Is there a registry entry that specifies the center of the desktop?