What exactly are you meaning for the XP welcome screen?
Are you meaning you are wanting the display of everything to look like Win XP? The blue colors at the top and bottom of the IE screen, blue welcome screen and such?
If so, go to "Start" then "Control Panel". Click on "Display". The Display Properties box will open.
In the "Themes" tab, click the check mark on the right side of the display theme line. A drop box will open from the line. Highlight "Windows XP" and left click "Apply" at the bottom right of the display properties box. Matter of fact your current display theme your running on now will be displayed on the theme line.
If I'm understanding your post right. Its probably set on Windows Classic currently.