Dell Precision M4800 touchpad

When my computer restarts the touchpad (that I keep turned off as I use a mouse) keeps turning itself back on. This is a recent problem in the past 4 months. Previously I could use the Fn F5 key and keep the touch pad off. Now the Fn F5 key no longer seems to control the touch pad and I have to go into the control panel every time my computer restarts. This is becoming a problem.

I am still on Windows 7- is this the cause?

Something else?