Pressing Fn + F9 Did Not Re-enable The Touchpad

I have a Toshiba Satellite A100-033 running Vista Home Basic. I mostly use the laptop as a desk top replacement and, as I dislike using the touchpad, I disabled it, and instead I use an external mouse via one of the USB ports. On my laptop the standard way to disable the touchpad is by simultaneously pressing the Fn key and the F9 key. However, to be honest, I am not sure whether I did in fact disable the touchpad by this means, or whether I used some other means (if it was by some other means then I have forgotten what this was). Recently I wished to re-enable the touchpad so that I could use the laptop outside the house without having to take my external mouse with me as well. However, I found that pressing Fn + F9 did not re-enable the touchpad and I now can't use the touchpad at all.

If I go into mouse properties (in control panel), this tells me that my synaptics pointing device is enabled. If I go into device manager and look at "mice", I am told that my touchpad is working properly. All this makes me suspect that the problem is not a hardware fault but that I have altered some setting, with the result that my touchpad is permanently disabled until I change the setting back to its original state.