As you probably know, Windows 7 does not come with USB 3.0 drivers included. I checked the ASUS website and beside the chipset drivers, you have controller drivers for USB 3.0 for the Intel and Asmedia controllers. The first two are a little confusing because they are designated a little differently, but the version seems to be the next sequence. Maybe the info on the download will tell you which one or both of those two you need, so it may require all three.
You might also check if you have the latest bios update.
Have you installed the chipset drivers?
You seem to have a USB modem. I do not know if it might be interfering, but you could try disconnecting it for testing.
That modem that you're seeing is my smartphone samsung galaxy s4, dunno why is labeled like that.Your Device Manger picture shows a modem, Samsung. If you do not actually have such a USB device, there may be a problem there. Try uninstalling it in the Device Manger.
The attachment is from an ASUS P8Z77-V Pro Motherboard. You can compare it to yours. The Unknown Device showing may be the Intel Management Engine which should be showing in the System Devices section and there may be a separate driver for it.