how do I set as a background on my desktop?

If you are referring to a picture that you created in RealworldPaint.com, then go to the location on your computer where you saved the picture and right click on it. On the drop down menu that opens, select "Set as wallpaper."

I would think you're trying to use the .rli file you made. You gotta save it as a .png or .jpeg (.png retain their qualityat the sacrifice of a large file-size whilst .jpeg is compressed and loses quality but has low file-size. .png's also have attributes allowing transparent pixels.)

In other words use .png.

Vista at least- does not support .png images as wallpapers though. I don't think XP does either. Probably because if you did have transparent pixels there is nothing for them to be transparent to. You can't see any deeper than the desktop.

i am currently using a .png as my desktop wallpaper in XP, so i am sure its possible in vista. on the desktop a transparent pixel will come back as either a black pixel or the color scheme.