We know the unsupported cards aren't going to perform well and there's nothing we'll be able to do to remedy it.
Using the program Swiftshader can successfully load the game even on extremely low powered machines.
Download the files from Sven’s site and read the “Read Me.txt” file.
This will contain the most current instructions for installing and setting up the wrapper.
Diablo III will block certain systems running the game if it does not detect a certain spec of video card.