If the driver is not compatible with Windows 7 or Windows 8.1 you will need to install it in the manual mode. First right click on the setup package and select Properties > Compatibility. Use Windows XP as a reference and then install the application normally. Reboot the computer, plug the modem and go to the Device Manager (Start > Run > devmgmt.msc). Right click on the item (yellow marked) and select Update Driver. Point the installation window to the folder with the modem software and drivers (usually Program Files**ModemNAME**) and that's it.