I have Windows 7. I placed the line:
@start /wait %windir%\ExtraPath\ScreenSaverName.scr /s & rundll32 user32.dll,LockWorkStation
in a batch (.bat) file, place it in a appropriate dir, and created a shortcut pointing to this, with the desired shortcut key.
In this line, \ExtraPath is the additional path under your win dir (usually this is \system32) where the screen savers are located, and ScreenSaverName.scr is the name of the desired screen saver itself.
It works perfectly.
Now I can press the shortcut keys to run the screen saver and lock the pc.
Thanks really a lot.