Mine is located here:
"C:\Program Files\Autodesk\AutoCAD Civil 3D 2011\Help\Civil Tutorials\Intersection-Assembly-Set_All-Crowns.xml
"C:\Program Files\Autodesk\AutoCAD Civil 3D 2012\Help\Civil Tutorials\Intersection-Assembly-Set_All-Crowns.xml
Civil 3D 2012 SP3 | Win 7 64-bit SP1
Xeon E5-1620 @ 3.60GHz, 16GB Ram | NVidia Quadro 600
Due to limitations i wasn't able to install the help but have it in a separate folder, i checked that folder and the hard drive and wasn't able to find it.