Vista - Touchpad disabling

Hi to All
I am using Vista 32bit on ASUS N50VN laptop, the very first day after installing my Desk top mouse (USB connection) using Mous properties I marked the box for "when using....disable touchpad" or something close to this statement, and TP was disabled and cursor stopped jumping around, after the secound power up touchpad was not disabled, cursor started to behave erraticaly and above all I CAN NOT SEE THE BOX anymore in Mouse properties, it has simply just just vanished and now both of my mouse are abled!!,Does anyone know what has happened here? and why the box that I marked for disabling the TP the first time has vanished?. Thanks a million.

It seems like a bit of a bug in the program for the control panel, this often happens when companies create their own software for this.
try this, go to windows update, see if there's an update for your touch pad or mice drivers (I say this because microsoft has a faster download) if its not there try the asus website, not there I suggest a system restore (but that's going a bit far) login as another user with administrative privelages see if its there.