There is a bit of a glitch when using older touchscreen hardware with windows 8.
Nearly all older touchscreen hardware is implemented as an mouse emulator. So when pressing on the screen it simulates a mouse click.
Windows 8 makes use of the touchscreen interface rather than the mouse interface for touchscreens, and the driver it installed for your touchscreen (if it installed one) may not be working too well with the hardware. If you install a driver separately for that touchscreen you may get back the mouse emulation for the touchscreen, but then some of the better options like gestures and sweep scrolling may not work well or at all in windows 8.
So what you really need is a touchscreen driver that is really a touchscreen driver (not a mouse emulator driver) for that model of touchscreen on your slate. If you know the touchscreen manufacturer you can maybe find a beta on their site for Windows 8? Find the touchscreen device in the hardware control panel and look up it's VID and PID to find the manufacturer if the driver page doesn;t already tell you. (There is a website somewhere that'll look up the VID/PID and tell you what the product and manufacturer is)
But.. may be slim chance. If not, try finding the normal windows 7 touchscreen drivers for it, that may help some, though not guarantee it'll be fully functional.