Add the following to your logon script:

<b>if exist %windir%\scrnsave.log goto scrsavok
regedit /s \\<ServerName>\<ShareName>\scrnsave.reg
@echo JSI > %windir%\scrnsave.log
:scrsavok</b>
where \\<ServerName>\<ShareName>\scrnsave.reg contains:
<b>REGEDIT4

\[HKEY_CURRENT_USER\Control Panel\Desktop\]
"ScreenSaveTimeOut"="360"
"ScreenSaveActive"="1"
"ScreenSaverIsSecure"="1"
"SCRNSAVE.EXE"="C:\\WINNT\\System32\\scrnsave.scr"

\[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\]
"NoDispScrSavPage"=dword:00000001</b>
The NoDispScrSavPage entry is from tip 0070, and will prevent the users from changing your settings.

NOTE: Change ScreenSaveTimeOut to be the time out that you want and SCRNSAVE.EXE to be the full path to the screen saver you want to use.