Hi Tommy,
Is the backing track on a DVD or CD? The reason I ask is that if it's on a CD then pop the CD into the PC and grab yourself a copy of
iTunes if you've not already got it, and then import the CD, much easier and probably better quality.
If the only way is to link up the DVD player and the PC then ensure you are plugged into the line input not mic input. From your description of the quality you were getting I'd suspect you were going into the mic input, or you need to adjust the recording level.
Hope that helps,
Chris