Python control of desktop properties

[Mediocre Person]

Hello, all.

I'm teaching Python for the first time to some high school students, and 
it's going well--Tomorrow's lesson: I'm going to show them how to use a 
list comprehension to simplify a task.

One of my students is interested in using Python to control his 
(Windows) desktop, and wants to write a program to change the desktop 
background or wallpaper. I told him I'd look into this, but I've had to 
admit defeat.

Can someone point me in the right direction, possibly post the simplest 
Python program that can accomplish this. I understand this won't be 
portable. At school, we use Win98SE; the student in question is using 
XPHome at home, and I typically use Gentoo Linux/KDE 3.3. If there were 
a single solution that would address all three environments, I'd be... 
well, shocked.

Merci beaucoup,

Nick.