My father experienced troubles trying to tether MiFi 5510L: unrecognized USB device. Apparently, a driver was needed to be installed. However, no specific driver should be required for Windows 7, because Novatel offers custom ones only for Windows XP. Letting the system to download one from Microsoft repositories needed a working internet connection. But that’s the modem who should provide a connection. You see, you need to be connected to become connected. Hilarious!
The problem solved when the PC was first connected using a different provider via a different modem (specifically, Kyivstar). The system was able to download a standard driver and allow tethering the 3G modem via USB.