My problem is this: waiting for Diablo 2 to start takes about five minutes. And, as I am waiting for the game to begin, the top left corner of my screen decides to remind me about the alphabet by going through its letters one by one. How can I get this thing to behave sensibly?

This will happen if you set the game to run on full screen - DirectDraw mode under Windows Vista or 7. Please run the video test and pick something else.