Nikhil,
I've nevr heard of Norton Power Eraser (NPE) as a removal tool if NRNR does not do enough. Normally the recommendation is to use the Norton Removal Tool (NRT) https://www.norton.com/nrt which is not the same as either of the above and does a more complete clean up than the NRNR although not as convenient..
Norton™ Power Eraser
Eliminates deeply embedded and difficult to remove crimeware that traditional virus scanning doesn't always detect. http://security.symantec.com/nbrt/npe.asp?lcid=1033