Surely, though, even if you prevent your brother from turning off the screensaver password, there would be nothing to stop him coming in before the screensaver has activated. The most secure way would be to get into the habit of locking the computer before you leave it (Shortcut Windows Key + L).
Anyway, this regscript should remove the screensaver tab from the display properties completely, thus preventing anyone from changing the screensaver properties. Of course, anyone with sufficient knowledge can easily undo it:
Please run Notepad and paste the contents of the codebox into a new file. Please do not include the word Code:
Code:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
"NoDispScrSavPage"=dword:00000001
Save the file to the desktop as
killscreensaver.reg and make sure the
Save as Type field says
All Files. Then go to the desktop and double-click on
killscreensaver.reg, and click
Yes to merge it with the registry.
If you need to undo it to change your screensaver settings (you'd better put this one somewhere safe

), the regscript is as follows:
Code:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
"NoDispScrSavPage"=dword:00000000
If you prefer, you can manually enter the info in the registry. To do so, click on
Start -> Run. Type
regedit and click
OK. Navigate to the following key:
Code:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
Change the
NoDispScrSavPage entry to 1 to disable changing the screensaver or 0 to allow it.