Sonar realtek hd audio problem!

Hi!
Here's the situation: When i have some audio loaded on one track (ex. drum) and i want to record a new track while playing back the drumtrk, i will always hear the drumtrack on the guitartrack (so when i solo the guitar track, the drum track is also recorded on the guitartrack). 
It's very subtle, but stil audible, and of course completly unwanted because i want to layer several guitartracks.

Is anyone having the same issue? I think it has something to do with the onboard soundcard of my laptop, but i have no idea how to get rid of that problem. 
Thanks a lot!