Uninstall Norton, problem solved.
In all seriousness though, what sort of "tasks" does Norton flag up during? I suppose these days even an 860 will get maxxed now and again.
There's also a "silent mode" within Norton, I believe you can activate it by right clicking the icon in the bottom right task bar, so I'd suggest when playing games to turn silent mode on, and then when you want notifying of stuffs, turn it back on.