try this. convert that background image to a BMP of the exact size of you laptop display. Now use that. Why this helps.
1. No more JPEG decoding.
2. No more image resizing.
The issue is known. There are workarounds.
When I move or minimize a window with just the desktop in the background, the old window image disappears slowly in strips starting at the top of the window.
This only happens when the desktop is in the back ground. If I have another program's window maximized in the background, I can move/minimize another window on top of that without trouble.
Running Windows XP SP3 on Thinkpad T60