Norton Ghost 14 backup questions

  I'm using the old Ghost 14 program to backup my PC's harddrive through a USB port to an external Harddrive.  I have the schedule set to backup the drive on a weekly basis.  I'm sure this is good enough to protect me from a major data loss.  If malware gets through NIS 2010, would it most probably get to the external backup drive also?  I don't change my PC's data very often and was trying to find a way I could perhaps schedule Ghost to run on the first of each month?  Also if I turn off the external harddrive, to protect the data, everytime I boot up, I get an error message from Ghost that it cannot find the external harddrive.  Is there a way I can prevent this message?    The program works great, now I'm just trying to fine tune it.