For whatever reason, seeing the default Windows XP screen saver when nobody is logged on isn’t always the most interesting thing to look at. Here’s a quick way to change which screensaver gets displayed:
Go to Start > Run and type regedit.
Navigate to HKEY_USERS\.Default\Control Panel\Desktop
Change the SCRNSAVE.EXE value from logon.scr to any other screen saver with an .SCR extension located in the C:\windows\system32 folder.
To disable the logon screen saver all together, in the same place as above, scroll down to “ScreenSaveActive” and change the value to 0. Change it back to 1 to enable the screen saver again if you so choose. This will require a reboot.