how do i disable ScreenSave?

hi,everybody!
i use windows embedded xp1(sp1) build a image with command shell,it run
fine, when no keyboard opration about 20 minute, it will auto come into
ScreenSave. i already setup the follow register,but it's yet;
[HKEY_USERS\.DEFAULT\Control Panel\Desktop]
"ScreenSaveActive"="0"------disable ScreenSave
"PowerOffActive"="1"--------don't close CRT when come into ScreenSave
[HKEY_CURRENT_USER\Control Panel\PowerCfg]
"CurrentPowerPolicy"="3"--------it's mean always on
whether ScreenSave ACTIVE IS a default set in XPE,and is about 20 minutes?
everybody help me !many thanks!