I went to the Dell support site but their manuals really suck to
describe how to use their product. With the identification of the make
and model, I found an online picture of the keyboard at:
http://images.anandtech.com/reviews/mobile/2008/dell-xps-m1730-x9000/dell-m1730-keyboard.jpg
I don't see any disable button near the touchpad. None of the Fn key
combos look to disable the touch pad. So Dell has not provided an
easy-of-use feature for their touchpad.
I can't tell from the above pic if those are 4 programmable buttons at
the top right of the keyboard.
http://images.anandtech.com/reviews/mobile/2008/dell-xps-m1730-x9000/dell-m1730-open-on.jpg
http://images.hardwarezone.com/upload/files/2010/04/4eae82cd6f.jpg
From those pics, it doesn't look like any of the media buttons on the
front edge will disable the touchpad.
So it looks like Dell didn't bother providing an easy disable/enable
button for the touchpad. Guess they didn't realize that uses of this
product might want to use external keyboards and mice.
So I'd focus on using Microsoft's devcon utility to disable hardware.
This is their command-line version of Device Manager. You could create
shortcuts (on the desktop, in the Start menu, or in a toolbar in the
Windows taskbar) to run devcon with parameters to disable or enable a
hardware device. No reboot should be needed to disable or enable a HID
(human interface device).
http://support.microsoft.com/kb/311272/fi
Use the regular graphical Device Manager (devmgmt.msc) to select the
device (the touchpad, in this case), right-click on it, select
Properties, and under the Details tab find the Hardware ID of the device
(select "Hardware ID" from the drop-down list). You use that string in
the 'disable' and 'enable' parameters to devcon.exe. You might be able
to get away with shortening the hardware ID to remove the REV portion.
For example, the hardware ID might look like:
USB\VID_06E6&PID_C200&REV_0044&MI_04
but maybe the following would work:
USB\VID_06E6&PID_C200
That way, if you update the driver, your shortcut to run devcon won't be
tied to a revision of the device. You can use the 'find' parameter to
make sure that devcon can locate the device by the hardware ID you
specify.