no wallpaper display on monitor

when i start my computer the selected wallpaper will show for a moment while in the start up process–when all has finished the wallpaper will not show–i have gone into display properties, theme installer, etc. to no avail–the colors will show up and the icons will change but the display will not show–can you help me? i have tried to find this topic in the msn/windows web site but i don’t see it. i have a windows 98