What is the reason for my laptop background is automatically change itself

[Guest]

Hello,
i set a backround in my laptop then shutdown my system after i on my laptop the backround was automatically changed what is the reason and how to solve the problem

 

[Herr_Koos]

It's a feature of Windows 7... It shows various backgrounds in a slideshow. To change this you have to set one specific file as your background instead of using one of the Windows 7 theme packs.