Change Default Windows Screen Saver

One way to change the screen saver that is run when no one is logged into a Windows XP box:

Quoted from Usenet, via Google Groups.
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=1993Aug25.015848%40atglab.atg.com&rnum=5&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26q%3Dset%2Bdefault%2Bscreensaver%2Blogged%2Bout%26sa%3DN%26tab%3Dwg:

"There is, in addition to the normal list of users (Administrator, etc),
a user ".DEFAULT".  The console settings for the .DEFAULT user are used
whenever there is no "real" user logged in.  But, since you can\'t modify
a user profile without logging in, it would appear impossible to change
the .DEFAULT profile.  

The solution is to use the Registry Editor (but with great respect and
care).  One of the first things I did after installing NT was to open
the Administrative Tools Group and add a NEW entry for RegEdit with
a command line "regedt32".  You can then click on this icon, or run the
"regedt32" command from a console window.

One regedit is running, select the HKEY_USERS on local machine.  Note
that the first entry is ".DEFAULT".  DoubleClick on this Key to give
a list of the sub-keys.  The "Control Panel" key can then be opened to
show a list of subkeys.  Here, you could change the color scheme used
by the login screen, if desired.  To change the Screen Saver, though,
you must open the Desktop key.

When you doubleclick Desktop, a list of key/value pairs appears on the
right panel.  The ScreenSaveActive should be set to 1 to enable the
selected SS.  The next entry, ScreenSaverIsSecure, should be left at
0, since setting this option probably make your screensaver ask for
a password, but who\'s password would it want?  The ScreenSaverTimeOut
is the number of seconds of idle time before invoking the SS.  I changed
mine from 900 to 60, since I thought 1 minute was enough time for me to
log in.

The real value to set, however, is the SCRNSAVE.EXE key, which should be
the pathname of the desired screensaver.  I changed mine from "D:\\winnt\\
system32\\sslogin.scr" to "D:\\winnt\\system32\\ssbezier.scr".  You can set
any of the *.scr files here.  (Somewhere in the NT manual, I think it 
said you could use screen savers from the IdleWild package if you put the
correct DLL in the system.  I can\'t find the reference, though.)"