Open the Registry (Start Menu >> Run, type in: REGEDIT then press Enter). Browse to the following key:
HKEY_CURRENT_USER\Control Panel\Desktop
In the right pane, look for value name SCRNSAVE.EXE (REG_SZ). Right-click on the value name and select "Delete" from the context menu.
In the same pane, look for value name ScreenSaveActive (REG_SZ). Double-click on the value name; in the Edit String box enter "0" (without quotes) in the value date field then click OK. Close REGEDIT.
Btw, I'd offer a simpler solution if there was one, but this is the only solution I could come up with. Let us know if it works or not...