shut down problem

I am running w/98 on my machine, ever since I installed Norton A/V it won’t shut down correctly, this was ok while on the old AT power supply, because before shutting down I got a screen asking me to “press any button” and then only did it offer theSafe to turn off option.
With the ATX case I get the same, but cannot turn it off at the button.What steps can I take to correct this?