There is no compatible driver for Windows 8.1, but you can make it work using the manual way. First install the software in compatible mode. Go to its partition in My computer and select Explore. Right click the setup package and select Properties > Compatibility. Choose Windows 7/Windows XP from the list and install it. Reboot the computer, then plug the modem and go to Device manager (Windowx Key + X > Device Manager). Right click the modem and select Update Driver. Point the installer to the folder where the software is installed (usually Program Files) and ignore any warnings Windows might show.
