Can Avast and Norton be ran on the same machine?
Will there be a conflict?
no 
Kindly read:
http://www.avast.com/forum/index.php?board=2;action=display;threadid=113;start=0
http://www.avast.com/forum/index.php?board=2;action=display;threadid=242;start=0
hi,
you can use both
shooter 8)
Yes/no! 
It depense on what you want to use of these two Programms.Only scanning with Avast will work, if no resident part of NAv or Avast is activ. You have to disable one Product(the part of the Product which will load at Windowsstart)