If you are already having problems please read the addendums 
first to remove old or non-functioning drivers. It is important to have them cleaned up and installed the appropriate drivers first before you plug in the board!
Download STM Defuse Demonstrator from here:
http://www.st.com/st-web-ui/
Extract the zip file and start the Setup. After a successful installation you will find all necessary files and drivers in subfolders of the STM program folder. C:\Program Files (x86)\STMicroelectronics\Software\
Before you connect the FC to your PC for the first time install this driver:
Virtual Com Port Driver
C:\Program Files (x86)\STMicroelectronics\Software\Virtual comport driver
\Win7 \Win8 (will also work for Win10)
Start dpinst_x86.exe for a 32bit Windows system
Start dpinst_amd64.exe for a 64bit Windows system
Follow the installation process and finish it. You can now plug the FC in and use the GUI.
Addendum: Removing previous Virtual Com Port Drivers
- Plug in the KISS FC
- Go to your Windows device manager, in the top menu select “View” the “Show hidden devices”
- You should see the previous STM32 virtual com port driver, usually marked with a yellow warning sign.
- Right click on it and select uninstall or remove, make sure you also selected “remove associated files”
- Unplug the KISS FC and start the procedure for the installation of the STM32 Virtual Com Port Driver as described above.
Before you connect the FC in bootloader mode (boot button pressed while connecting the USB) to your PC, please install this driver:
Bootloader Driver
Correct Driver for DFU Mode
Wrong Driver (mostly Zadig)
C:\Program Files (x86)\STMicroelectronics\Software\DfuSe\Driver
Start dpinst_x86.exe for a 32bit Windows system
Start dpinst_ia64.exe for an Intel 64bit Windows system
Start dpinst_amd64.exe for an AMD 64bit Windows system
Follow the installation process and finish it. You can now connect the FC in bootloader mode and flash the FC with Defuse.
Addendum: Removing previous Bootloader Drivers
- Plug in the KISS FC in bootloader mode (with the boot jumper bridged or boot button pressed)
- Go to your Windows device manager, in the top menu select “View” the “Show hidden devices”
- You should see the previous STM32 Bootloader driver at the bottom of the list under “USB devices”, usually marked with a yellow warning sign.
- Right click on it and select uninstall or remove, make sure you also selected “remove associated files
- Unplug the KISS FC and start the procedure for the installation of the STM32 Bootloader Driver above.