I have an mx 300 and it works fine. I downloaded and installed service pack 5, and then went to A3d's site and downloaded the drivers there because when i used the cd, it gave me an error. Here is the actual link i downloaded from- ftp://ftp3.a3d.com/pub/Public/Drivers/Vortex/nt2.04.06.zip
i just extracted the files to a folder and folllowed the readme that was in there and it works great! Maybe this is what you did but i thought i would try to help