The order in which your drivers are installed may well determine if your touchscreen will work. To fix this issue, you need to load the needed drivers on a flash drive or another machine. I suggest <h>www.toughbookdrivers.com/drivers/cf-29/</h>
First, restart your computer in safe mode (pressing [F8] as you are cold-starting up).
Then, using CONTROL PANEL, remove all drivers (Video, Audio, Mouse, Peripherals, etc)
Finally, install the Touchpad/Touchscreen driver FIRST. Install then video, then audio, then the rest....EXCEPT save the LAN and WLAN drivers, respectively, for LAST. If you have GPS, add after LAN and WLAN drivers are installed.
If this doesn't work, it's likely your touchscreen card went bad...it is a weak link with these units...especially the Mk IV's or V's.