uses
shellapi;

procedure InstallScreenSaver(const FileName: string);
begin
{ Set this screensaver as default screensaver and open the properties dialog}
ShellExecute(Application.Handle, ‘open’, PChar(’rundll32.exe’),
PChar(’desk.cpl,InstallScreenSaver ‘ + FileName), nil, SW_SHOWNORMAL);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
InstallScreenSaver(’c:\YourScreenSaverFile.scr’);
end;