That's what I didn't understand as well. When exchanging cards, the board must reset to On-board, but not switch to discrete AGP automatically (recent ones do it, though). However, when the MX440 is installed no display is given, for what I can understand, trough the card's VGA connector, no word about the rear panel I/O.
This would only make sense to me if the OP didn't clear the CMOS between changing from the Radeon to the GeForce. Because if he did, the 1st display would always be the on-board GPU, as those board usually do by default. When that happens, plug the VGA connector to the rear panel, it should display something, change the BIOS settings, save, reboot, now plug the VGA connector on the card's plug.
But so far, that doesn't seem to be what OP has done, at least from what he has written.