I work with corporate network but I have adminstrative rights on my computer. The net administrator changed the desktop wallpaper on all computers in the network to place an ad on it. when I tried to change that wallpaper I found the wallpaper dialogue box frozen and no wallpaper could be changed that way. Is there a way to manipulate the wallpaper to override the network change?

If your administrator decided to give all the workstations in his network a default wallpaper of his choice, it is like it is. Ask your Administrator to let you choose your own wallpaper or ask him for the reason why.

Unless you're a Domain or Enterprise Admin, you can't override a GPO, or exempt your computer from one. Life's more painless for the brainless.

If negotiations work I wouldnt post here. How do I know if my rights are enough to make a change?

If you were unsuccessful in your attempt to change the wallpaper, that pretty much says it. I would think you should know at what level your Domain account is set. Guessing by the way you're phrasing your situation and question, I would say you do not have an account in the Domain or Enterprise Admin Groups. Life's more painless for the brainless.

What I did was to disconnect the network cable, restarted the computer, and the freeze on the desktop dialogue was gone. I noticed that the said wallpaper reapears everyday at noon. All I need to do is to disconnect the cable at that time to avoid it. By the way, that wallpaper contains an ad for the corporation which means it is a method with poor taste to advertise. It is like putting a flyer in your face to make you read it. A stupid way to do it...

I'm sure Management doesn't feel that way. Life's more painless for the brainless.