OpenGL Newbie question

thanks in advance for any help!  I'm trying to use

  glOrtho(-200.0,200.0,-200.0,200.0,-3.0,3.0);

and then draw a line using

    glColor3f(0.5,0.0,0.0);
    glBegin(GL_LINES);
    glVertex2f(-100,0);
    glVertex2f(100,0);
    glEnd;

The line appears, but it goes from one side of the form to the other.  Even
when I use:

    glVertex2f(-10,0);
    glVertex2f(10,0);

Only if I use:

    glVertex2f(-0.5,0);
    glVertex2f(0.5,0);

does it start 1/4 in from each side.

Here is the core code:

  FillChar(pfd, SizeOf(pfd), 0);
  pfd.nSize      := SizeOf(pfd);
  pfd.nVersion   := 1;
  pfd.dwFlags    := PFD_DRAW_TO_WINDOW or PFD_SUPPORT_OPENGL;
  pfd.iPixelType := PFD_TYPE_RGBA;
  pfd.cColorBits := 24;
  pfd.cDepthBits := 32;
  pfd.iLayerType := PFD_MAIN_PLANE;
  glDC := getDC(Handle);
  FormatIndex := ChoosePixelFormat(glDC, @pfd);
  GLContext := wglCreateContext(glDC);
  wglMakeCurrent(glDC,GLContext);

  glOrtho(-200.0,200.0,-200.0,200.0,-3.0,3.0);
  glEnable(GL_DEPTH_TEST);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity;
  glEnable(GL_CULL_FACE);
  glCullFace(GL_BACK);

thanks,
mike