If it says cannont delete, check the path of the file, very well could be that the file doesn't exist as it was already deleted the second norton found it (don't ask me why it doesn't say it deleted it, but I find that Mcafee does that as well)
As for preventing spyware and junk, best way is to be proactive. Don't surf stupid sites, ones with tons of pop ups. Crack sites, porn sites, sites you don't know very well, any site that asks you to install anything. NEVER click "yes" when anything asks to register or install, allways click the "X" in the upper right hand corner. Firewalls are allways good, BlackIce works well for me, let me know and I'll hook you up with a copy. Virus scanners like norton and Mcafee are good for viruses, they not the greatest for preventing spyware and pop ads and crap like that.
1.2.1 Ball Pythons
1.0 Cali King Snake (Weebl)
0.0.1 Black Breasted Leaf Turtle (Hootie)