Simplest OpenGL program ever -- not working...

You're drawing a line that is 1 pixel across and 1 pixel up. Also, GL_LINE should be GL_LINES. Change:

glBegin(GL_LINE);
glVertex2i(0, 0) ;
glVertex2i(1, 1);
glEnd();

to

glBegin(GL_LINES);
glVertex2i(0, 0) ;
glVertex2i(100, 100);
glEnd();

and it should work.