Hi,
I have MyOrgan working in Vista just fine. I have no idea about the e-mu 0404 but if you have ASIO drivers for it or can use the ASIO4ALL drivers with it (the most recent version is Vista supported) you shouldn't have a problem.
Is there anyway that you can try it out on the laptop before you buy it? I don't anticipate any problems, but if you can test before you buy it would help you feel more right about the purchase.
Graham