Vista Tutorial - Desktop background (wallpaper) keeps reverting back to imageHPSproutv2- Vista Home Premium

Hi,
Please can someone help me with a fustrating issue I have with setting
the desktop background in Vista Home Premium.
I have just purchased a HP Pavilion DV6799EA Special Edition in the UK
with the aforementioned OS. During the installation I was promped to
choose a desktop background and I chose the so called special edition
background which matches the chocolate colour of the laptop lid. See
the link from HP site.

http://h10010.www1.hp.com/wwpc/uk/en...-81657871.html

The problem I have is that when I change the desktop backgound
(wallpaper) and restart the laptop the dersktop has reverted back to
the desktop I chose during installation. How can I get the laptop to
keep my newly selected desktop?
Hope you can help!

By the way, after I restart the laptop and go back into Desktop
Backgounds the desired wallpaper appears immediately without even
selecting it with a mouse click on the radio button!