In XP pro SP2, some client's wallpaper wasn't loading completely, showing only the top 10% of the screen. Occasionally, it was just a plain color with no background picture at all. One would have to manually refresh (F5) the desktop so that the full picture will be complete.
After some research, I find this seems to work:
Enable Turn on Classic Shell:
type gpedit.msc in Start->Run,
Enable "Turn on Classic Shell" in User Configuration=>Administrative Templates=>Windows Components=>Windows Explorer.
[@more@]