How to remove blackscreen wallpaper from window xp

Try this program:http://www.softpedia.com/get/Tweak/Unins... and disable automatic updates: START-> CONTROL PANEL-> AUTOMATIC UPDATES -> CHOOSE THE OPTION -> Turn off automatic updates <- ;-) .....

You are getting the notification on your screen because your copy of Windows is less likely to be genuine and has failed the WGA validation process. Such notifications do not pop-up if a user is using a genuine copy of Windows. You are getting your desktop background as black screen because if a copy of Windows XP fails validation, the desktop background gets automatically changed to black screen. Even if you attempt to change it to a one of your choice, it will get automatically reset to black background every 60 minutes till the time your copy of Windows passes the validation process.

The only way to get rid of the notification and the black desktop background is to use a genuine copy of Windows. Thus, it is recommended to check if the copy of your Windows is genuine. If it is not, you need to buy a genuine one to resolve your issues. For more details, you can refer to the following Microsoft support link:
http://support.microsoft.com/kb/905474

Once you have validated your copy of Windows, you can refer to the following webpage to change your desktop background:
(Important: Following link is of a third-party website. It is recommended to update your security software thoroughly before clicking on the link.)
http://www.wikihow.com/Change-Your-Desktop-Background-in-Windows

Hope this will help you.

GuruAid.com

It could be virus. Try running a full system scan.