My System is Dell 14R 5420(laptop) equipped only with USB3.0 Ports - and the way i was able to Get USBPassThrough working in W7Sp1x64 with Workstation 9.0.1 is as follows:
1) Remove Previous versions of Intel USB (xhci) drivers and restart System
2) Install Intel xhci verison 1.0.6.245 Drivers using DEVICE MANAGER --- and not the Installer Binary Image
If i use installer - USBPassThrough won't work and if Installed "Intel USB3.0 eXtensible Host Controller" and "Intel USB 3.0 Root Hub" Device Drivers using Device Manager(devmgmt.msc) interface --- then all Works.
USBPassThrough tested with WLAN, WebCam, Bluetooth, USB Mouse and USB Flash Drives (all tested Devices are USB2.0 capable only)