I can, did, and will again state that for the program he is using, the audio solution he is trying to use with it is insufficient. All he has to do is read the help files in the program and this is very well explained in there.
I have been using this program since the days of Cool Edit (yes...BEFORE Cool Edit Pro). Adobe bought out Syntrillium Software, and some of the engineers chose to stay on, and released Adobe Audition 1.5 as a rebranded Cool Edit Pro 1.0. Adobe Audition 2.0 was a beefed up, better multi-track program, which had some bugs, but was a spin in a different direction. Adobe Audition 3.0 is the first of the softwares designed to be used with ASIO Low Latency Drivers, which his audio solution DOES NOT SUPPORT. The lowest end devices on the market that have decent ASIO support are Creative Sound Blaster X-FI products. Even these, when in Audio Creation Mode, do not support External Monitoring, which is required to eliminate the issue he is having.
The devices I listed are what he needs to look into to use this program effectively. I have been recording my own stuff in my own studio for over 15 years now, and in the digital age 12 at least. This program has been my bread and butter since the word go. I have grown with the software and seen it go from a great audio editing tool to a powerful DAW. When AA4 comes out, the setup he is trying to use would not work at all, as the device support list I'm sure will get tighter, as Adobe is designing this to be used by higher end professionals, and gearing Soundbooth for home casual users.
I think I am quite qualified to speak on how to use Adobe Audition 3.0. I myself don't even know ALL of the cool things it will do, but know most of it. Nvidia sound is nothing new, as it was on the NV1 back in the day, but dropped due to bus and other issues. It is simply an output device. And even on Nvidias page, only the new GTX570, 580 support bitstream, the rest are Analog out PCM. It is not a true DSP on the video card, nor does it support ASIO. Realtek Audio chips do not support ASIO onboard either.
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To the OP, one thing to note, in a pinch, go get ASIO4All. This may help you out until you can get a better solution. This driver takes Windows WDM drivers and spins them into a form of ASIO, and it indeed works, but not on a large scale. You will be able to get 7 tracks in sync depending on how powerful your machine is. ASIO4All is free, and located
here