I have seen only a small number (2-3) that I can recall, where someone did indeed have some sort of conflict where turning off their on-board sound resolved it.
The far more usual things (in my opinion) that I have seen is where folks:
1) Had ASIO4ALL installed from some attempt at using it, but left it on their machine after moving on to the ASIO drivers of an actual audio interface, where ASIO4ALL somehow had interfered with the other ASIO drivers.
2) Were having issues trying to use ASIO with multiple audio interfaces from different manufacturers at the same time.
3) Were using the ASIO drivers of their audio interface, BUT also had the Windows Default Audio Device trying to access the ASIO drivers of their audio interface, and conflicts arose.
4) Had ASIO drivers available for an audio interface, (which others were using successfully), but for some reason were using WDM/MME (non-ASIO) drivers, and getting poor performance. (please note that for some, better success has been reported using WDM rather than ASIO for their particular audio interface)/
Some folks also choose to go into Windows Device Manager, and disable their on-board audio drivers there, rather than going into the BIOS.
Others, like myself, run using the ASIO drivers for their audio interface, and have their Windows Default Audio Device set to the on-board audio, and then run the output from the computer's audio to 1 of 3 places: 1st - a set of separate speakers than what the audio interface uses, 2nd - they feed the computer's audio output back into the audio interface into an input channel on the interface (sacrificing an input for the sake of better sound than computer speakers), or 3rd - (and this is what I do), I use multiple HDTV's as display monitors, and I select an HDMI output for my Windows Default Audio Device, and it sends the audio through the HDMI cable to one of the monitors - using its built-in speakers.
I think that when the original poster becomes available, and perhaps with your assistance, as well as others here in the forum, that we can methodically go through a review of the connections, settings, and such, and likely get his computer up and running properly. The fact that there are not bunches of people posting about Sonar failing to produce audio output is a good indicator that the issues are local to that computer and its setup/configuration for audio streaming with Sonar, and therefore quite likely able to be resolved with some interactive guidance.
There will still be a learning curve, but really, for basic recording, playback, and editing, many of the functions are the same, it's just a matter of remapping the 'how to do them' that is needed. Newer features can be learned after figuring out the basics of it all in the new user interface.
Bob Bone