Fastlane's right, folks will need to know a little more about this system. What type of audio interface, for one. Also, whether you are using your system's built-in interface as the default Win audio interface, or if you're trying to use your 'pro' interface for both.
(I've found it works well for me to keep my built-in audio for default system use, vids and the like, and just access my 'pro' interface by selecting its drivers in Sonar's Driver list. That way, no other software is contending for my outboard interface. I do switch the default to the good interface for listening to browser-based subscription streams, though. When I switched to a service with all 320 kbps streams, I found I could notice the difference between the $2 sound chip in the computer and my once $800 outboard converter. Imagine.
Also, have you been able to use the interface with any other software or does it produce these awful noises with anything.
This is likely to be both encouraging and simultaneously frustrating, but I feel fairly certain that when things are all sorted out, that you should be able to have a considerably smaller hardware buffer size (~400 samples is pretty generous as a rule; I have an old, single core Pentium and am able to get 128 sample buffers going with my MOTU 828mkII at 44.1 kHz -- although 64 samples is a total no-go).
Since you're new to Sonar, I'll also point out or remind you that in addition to your hardware driver buffers that buffer the interface from the computer system, there are also cue/monitoring/playback buffers you set from inside Sonar's audio options.
The minimum setting (in milliseconds) is generally the temporal equivalent of your hardware buffer [in my case 128/441000 = ~2.9 ms] -- but that's the minimum.
Depending on what kind of plugin and virtual instrument load you're putting on your system, you may need to increase the buffer size from time to time, maybe a fair amount if you have a complex mix with a lot of processing.
(Which is why, with my old hardware, I make plenty of use of Sonar's mostly quite convenient freeze function -- or, sometimes, if I need to cut live MIDI and so need the lowest possible latency, I'll just do a quick bounce of all the basic tracks, temporarily archive them so they're not a load, and work from the 'temporary' bounce. It's faster than freezing a bunch of tracks. (Maybe they improved that in the X generation; I'm on 8.5.)