Installing NIS 2009 into Vista???

I’m going to install NIS2009 into personal computer with Vista home.  First Norton product.  Not very computer literate!! I currently use free AVG 8.0, Superantispyware and CCleaner.  Do I remove those items?  How about Windows Defender?  Do I close all items? Will that not allow viruses to come in while I donwload NIS2009.  Should I make a CD back-up first just in case.  I want to use this product as it should be used but I am fearful I may mess up a pretty darngood running pc.