There is another trick to put a background of your own choice on windows xp for the welcome
screen. It is very interesting trick and you can use it easily. follow these instructions for this trick.
1.  Open your browser and type www.google.com.
2.  In search bar type “logon studio” and press “i ‘m feeling lucky
3.  you will see a webpage. http://www.stardock.com/products/logonstudio/
4.  Press the button download near “logonStudio”
5.  On the next page you can see heading “LogonStudio For XP Download“.
     Click on download button found right side of this heading.
6.  Save this setup file and double click to install the software.
7   In this software you see 3 available logos and also you can download more logos from the link
      mentioned below. Select any logo and click apply.
 8.  Done.