If you are still having problems with dropouts:
1. There is a TON of info out there on the web for these kinds of problems for XP and Windows 7.
2. DO adjust your buffers up AND REPORT BACK ON THIS POST with the results - whether it worked or not.
3. Download a small program called DPC Latency Checker. This is a free utility that will tell you what your current latency is, as well as your maximum latency during that session of running DPC Latency Checker. If you are getting latency 'spikes' above 1000us, you will most definitely get audio pops, crackles, or dropouts. If you are seeing these spikes in latency, you will need to go through identifying and mitigating causes of the spikes. Things like anti-virus software running, a bunch of other services running that are not needed for recording sessions, and that sort of thing can be causing you trouble with dropouts. If ANY of these kinds of things are in fact causing your dropout headaches, then switching to another DAW suite will do NOTHING to get you past dropouts, as the dropouts are not caused by the DAW, they are caused by other factors present in your hardware/software environment.
4. Now the good news - even though identifying the fundamental underlying causes for dropouts is one giant pain in the rear, it is something you will only have to do once for your machine.
PLEASE PLEASE report back on what you find when you run DPC Latency Checker. There a folks here who will invest time in trying to help you, but only if you show a combination of thoroughness in describing your EXACT software/hardware environment and that you also show a willingness to try incorporating the help that IS offered to you. This is a problem that MANY MANY people have faced, with Sonar as well as with virtually every other DAW out there. Many of us here will work with you to get past this.
Here is a link to download DPC Latency Checker:
http://www.thesycon.de/dpclat/dpclat.exe Bob Bone