it will be highly likley that this does not have anything to do with your fan, in fact i dont see anyway possible that a different fan can do this.
I have seen this msg before, it happens when the monitor is disconnected from the video card, but still has the power cable connected to the screen,
you should check the connections between the video card and the screen, and take out the video card and put it back in again as you most likey would have bumped the card when u were installing the new fan.