brundlefly
This isn't a SONAR issue, it's an external mixer routing problem. What you need to do to fix it depends on what I/O connections you're making between the audio interface and the Behringer.

I'd lay odds that's the answer.

I have a problem on an Asus notebook having involuntarily upgraded to Windows 10 (don't know what happened - just happened spontaneously and I've had headache after headache since with just about every piece of software I have installed - even MS Office - anyway...) Now the audio track I want to record on records everything from the previously recorded tracks as well as what I actually want to record on the track - this is not bleed this is actually recording at full volume. I'm using an Allen & Heath ZED FX as an interface. I had no problems at all before the upgrade. Man those Microsoft guys really know how to ruin your day. I would appreciate any suggestions 

I'm reluctant to reply to a old thread. You should start a new thread, but I'll be nice and try once again. 
First :
 I'm using an Allen & Heath ZED FX as an interface
 
I would imagine they never supplied proper ASIO drivers for Windows 8 and now your on 10. 
You would be best off to purchase a proper audio interface. The USB of those boards is not really designed for working properly with a DAW. Either you have your mixing boards routing haywire or there is now a "what you hear" happening just like Dave has said in # 9. 
 

Derek, it might just be easier to roll back to Win7/8 (I assume it was one of those and not XP).
 
http://windows.microsoft.com/en-us/windows-10/going-back-to-windows-7-or-windows-81
 

Thanks for the quick response and my aologies for contravening the protocol. I'm a first time poster so I plead ignorance. On the A&H not being designed for work with DAWs that's just not the case. I've used it with Vista, 7 and 8.1 with no issues. They recommend MME (32bit) not ASIO. The only difference here is the unwanted upgrade to Windows 10 from 8.1. It worked fine before that - a week ago. I've updated the sound card driver and uninstalled and reinstalled Sonar to no effect. Any idea how to turn of "What you hear" in Windows 10?