The Realtek 7.1HD sound drivers do my head in. I have a mobo with this sound on board and connect it to my Creative THX Gigaworks G550W 5.1 system via separate leads as the G550W has no optical input.
The problem i have is that i cannot get it to work correctly in 5.1 and instead i have to use it in 7.1 with the rear speakers connected to the side speakers socked and disable the rear speakers in the software. It works fine in this mode for some reason but in 5.1 mode the rear speakers don't work at all even if i have everything connected correctly.
I might not bother downloading v2.16 as the set up after is a real hassle.
Creative has released an updated Version 1.25.10 of the ALchemy software for X-Fi and Audigy sound cards under Windows Vista. Note that the ALchemy download is found under the Application link on the driver page for your particular sound card.