vistaxp

as you can see, i am using vistaxp. so far everything works great except for when i set a new desktop wallpaper. i like to have the image centered (with black around the edges, don't ask i just like it that way, looks better in my prospective). but, it is automatically switches the border to be a blueish-gray. even after i set it back to black, it changes back the next time windowblinds loads. why is that, can i change the settings so it doesn't change back? i tried but to no avail.

any help would be helpful, thank you for your time

-nightslayer78