Background programs automatically minimize my full screen game win

I am playing WoW and having a lot of problems with other programs like Yahoo
Messenger and Norton Internet Security automatically minimizing my full
screen game window. If someone sends me a message on Yahoo, or if NIS stops
an attack on my computer it takes control of my computer, minimizes my game
window and displays a message box for me.

Its messing up my game and its also corrupting my WoW game account and
causing the game to lock up. I had to contract Blizzard support to have them
re-program a few things in my account because it was completely messed up
when it was minimized. My character position was lost and the game didn't
know where my character was standing in the game because my position is based
upon the screen resolution.

I need to stop this from happening and I don't know what Windows settings
will stop this.

I need to stop other programs from taking control of my computer, and
changing my active window when I am running in full screen mode.

Thanks.