ok i am not assuming anything but supposing that your pc is pnp (plug and play) then windows will try and install its own driver for your usb modem. To install the correct drivers you will have to insert the cd before plugging your usb modem in, then install the correct driver for your modem once the installation is complete insert the usb modem/device. If there is still an error or your device is not reconized then check the device manager let me know how it goes
