Not all computers can utilize the usb option. Ensure that both the ethernet and usb cords are not both plugged in. You can only use one or the other. Also ensure you use the installation cd when using the usb cord
I have not been able to get the USB option to work with any Linux OS. But yes to windows and mac. Also understand that you have to have a router in addition to your modem if you want to use more than one computer at a time. You cannot provide internet to one computer through the USB and another by Ethernet. On one computer you can use ether the USB OR the Ethernet not both. This is a very good modem and supplemented with a router is fantastic. The installation CD is to install the drivers in windows or mac to make it communicate with the computer"make it work".