The driver is used to allow your device to connect to a Windows computer via a USB cable in order for the computer to communicate and recognize your LG Viper.
LG Viper(LG LS840) USB Drivers
This package includes the LG United Mobile Driver revision 3.8 for Windows XP, Vista and Windows 7 OS. Once the download is complete, double-click the installation file and follow the instructions provided in order to update your drivers. It will allow you to connect your LG phone to PC.
Also, You can download the LG Vipers USB Drivers Ver 3.7 Here