Second Monitor troubles with Vista Home Premium

I have recently purchased a new HP Pavilion Notebook with Vista Home Premium
on it. I have a second Monitor, color, made by Trinitron in 1998. It worked
fine as a second monitor on my old laptop running XP.
When I connected it to my new laptop, it works fine while it is booting up,
showing everything fine. Shortly after it reaches the point where my desktop
has appeared, the picture starts blinking off every few seconds. It is not a
flicker, it actually blinks off for a second or 2. Between the blinking, it
looks like it is show the desktop on the second monitor the way that it is
supposed to. I can move my mouse back and forth and move items back and
forth between the 2 monitors the way that you should be able to. When you
choose to shut down or restart the laptop, the blinking stops as the laptop
shuts down, and you can see the laptop shutting down on the monitor with no
problem.
I was thinking that since the monitor works fine while booting up and as
soon as you choose to shut down, it might be a problen with Vista. Any
ideas? Thanks!!!!!!!!!!!