ive had a bad experience with norton.

not a really bad one, just the fact that it said, "would you like to update norton security suite"

then it updates, by itself, then tells me that windows firewall must be turned on immediately or my computer could be at risk.
my computer turned out to not only at risk but infected with 37 viruses.
i turned the computer off, downloaded the CA security trial on my friends computer.
next day i put it on the computer and BAM, no more virus, except vista of course.