This is really a marketing scheme. You see the logic behind this product is that every multitasking OS limits every single thing you do, so it can control and hand out resources accordingly. If the OS didn't do this, processes would get out of hand and eat up tons of resources that it shouldn't. However, even though there is a flag in the registry to open up more bandwidth it really does nothing. Your OS can't control bandwidth.
Furthermore, there are also instruction sets in the device driver itself. If you run windows, every driver service running actually runs at root level, making it a very high level process and giving it carte blanche over other processes. In OSes like Linux/Unix/OSX the OS kernel is actually considered a mini kernel, and the root processes and driver processes are different, they aren't given root level access so to speak but act as high level processes. Of course I am no developer or software genius, but that is how I understand them to work.
So, if you have a piece of hardware with sufficient power (hence the processors and what not on the super speedy NIC) and the proper drivers giving it more power to send and receive packets faster it will do so. However, I digress, that this is probably not going to give you the performance increase you would expect, and I would also say it is probably not even nearly worth the cost of the card.
If you want better connection rates on your internal network, get a giga switch with gigabit cards in your clients and run cat 6 cable (since it has higher bandwidth over cat5e) to your clients.
Now of course that doesn't mean it doesn't exist, I just can't find anything about it.
