Unable to connect my BBB via usb

I have netbook with windows 8.1.
I tried connecting it via usb with BBB but it stays undetected.
PWR is on
USR0 is blinking
USR2 is blinking very fast or the light is very weak.
I downloaded driver and installed it.
I tried on a PC with windows 7 same thing happened.
Any suggestion are welcome. Thank You.