I've seen many posts on getting the USB Controller to work properly with windows xp and parallels, but none that worked for me. I could not get a USB stick recognized in windows because the USB controller had a yellow question mark. I tried removing the device from the VM and restarting but got the same problem. My solution was simple and worked well. I removed the unknown USB controller device in windows, using the hardware devices window. Then I simply refreshed the window (actions -> look for new devices). It then found the USB controller and installed the driver fine. Note that prior to this I had several devices installed properly under the USB section. The one giving me trouble appeard to be the USB 2.0 driver. Hope this helps someone!
