How to disable screen saver in Windows XP?

One of the easiest things that you can do to remove screen saver is to simply select none from the Screen Saver tab of Desktop properties window. This should help. Doing this would be all that most of us would ever need for those few who want to go one more level, here is what you can do. Windows has a default screen saver called login.scr, which runs even if no screen saver has been selected. There is a potential security risk here as login.scr can be removed and replaced with malicious screen saver with system priviledges.
To resolve this, Open registry and navigate to [HKEY_USERS.DEFAULTControl PanelDesktop] and look for the data key "ScreenSaveActive". Setting its value to 0 would disable screen saver (you can always enable it by setting it back to 1). You may as well change the login.scr that is goes as the value of data key 'SCRNSAVE.EXE' .Try clearing out the value for 'SCRNSAVE.EXE' to completely remove the screen saver or replace it with some thing of your own.