I got an USB touchscreen. The touchscreen on my device is a PenMount 6000 USB. When running dmesg, this is what I found about it:
<6>[ 4.033918] input: DIALOGUE INC PenMount USB as /class/input/
input6
<7>[ 4.060448] evbug.c: Connected device: "DIALOGUE INC PenMount
USB", usb-0000:00:1d.7-4.1/input0
<6>[ 4.060456] input: USB HID v0.01 Mouse [DIALOGUE INC PenMount
USB] on usb-0000:00:1d.7-4.1
<6>[ 4.066725] usbcore: registered new interface driver usbhid
<6>[ 4.070042] drivers/hid/usbhid/hid-core.c: v2.6:USB HID core
driver

This says it's registered as a USB HID. Information from /proc/bus/input/devices
I: Bus=0003 Vendor=14e1 Product=6000 Version=0001
N: Name="DIALOGUE INC PenMount USB"
P: Phys=usb-0000:00:1d.7-4.1/input0
S: Sysfs=/class/input/input6
U: Uniq=
H: Handlers=mouse0 event6 evbug
B: EV=1b
B: KEY=30000 0 0 0 0 0 0 0 0
B: ABS=3
B: MSC=10

It is registered as /dev/input/event6.

Now I want to write my own driver for this touchscreen. It looks like it's using an other driver. Can I write my own and will it use my driver instead of the standard USB driver?

You don't say anything about what version/distro of Linux, but did you Google for this? Or visit the PenMount website?

http://www.penmount.com/down_2_1.php

Lots of ready-to-go Linux drivers for your device......

My distro is not mentioned. But the main thing is that it's recognized as USB hid. If I would write my own driver with specific VendorID and productID, will it overload the other 'driver' ?

And how do I know what kernel driver a device uses? What code will be called at the moment when I touch the screen.

All the USB HID driver code is located in /drivers/hid/ from the root kernel directory tree. Thankfully, it's quite easy to understand although you may have to do some Googling first (primary about the HID spec if you don't already know it).

But it looks the USB core now redirects the touchscreen to the usb hid driver. How can I redirect it to my own driver?

And you still haven't mentioned it. There's Fedora, SuSE, Slackware and Ubuntu on their site, as well as the source-code driver, ready to compile and use.

I'm using Android. I need myself a kernel driver. But I'm almost there at the moment. Just need to get the correct X and Y values from the device. I yet don't know what to do with the data I'm getting in from it.

In the installer for Ubuntu:
Now are they malicious, or just plain stupid?