You can find the USB drivers for the AMBrc
HERE
Another problem, the software your using has to support the USB protocol. I'm not sure if Laps Free does. JLap does but RC Scoring Pro does not (according to their website).
Also, if you allowed Windows "found new device" wizard to install a generic driver for the AMBrc it will have to be uninstalled. After the uninstall reboot then plug in the decoder again and when you get the wizard direct it to the folder where you have the USB driver saved.
Again if the software does not support it don't bother. If your computer doesn't have a serial port then you may have to use the serial/USB adapter. Not all these adapters are compatible with the AMBrc. RC Scoring Pro recommends one on their website.
One more thing: AMBrc3 does not have USB. Only Serial (RS232) and TCPIP (RJ45).
Hope this Helps!