I have an HP Elitebook 840 running Windows 7 Enterprise (64-bit) that is not detecting my external monitors. I have downloaded the latest drivers for the monitors. When I first plug it into the USB port, it flashes on, but then it doesn't detect it. I have tried fn+F4 and "setup computer to use multiple monitors". These monitors work well with my other laptop (using the same cables). The monitors I am using are HP EliteDisplay S140u and HP U160.