Windows Welcome Screen

Another solution to change the screen:

download cmdasuser.exe from mickeysoft
logon into windows using an administrator account
start->run->cmdasuser localsystem<enter>
ctrl+alt+del->task manager
kill all explorer.exe processes and dont minimize the dos window which says localsystem in the title.

click the dos windows
type explorer.exe<enter>

The localsystems desktop is loaded.

Now you change with desktop->rightclick->properties->desktop the desired desktop. When you are finished, reboot your computer. Et voila

There are programs like StyleXP and Screen Booty which allow you to change the look but caution is advised as any errors might just cause you to have to do a fresh install or repair. These are both for XP.