I too just bought this and while the ps2 controller works, gamecube and dreamcast do not. Who uses 32 bit operating systems anymore. I am an admin on three emulation sites with about 200,000 total users. After the experience I had with the top guns and now this (I did not care about rumble support), I will be telling all of our members to stay far away from EMS products. The lack of support is just appaling.
If PS2 controller works, but GC/DC controllers don't, the adaptor may be defective. For this case, you may consider to send it back to us, we would repair / replace it free of charge and you just need to pay for the postage. For details, please email to us at firstname.lastname@example.org. Thanks.