Sorry to hear about your problem. Are you happened to have Asus motherboard? For your amusement, read my thread on Microsoft site. They combined several threads in to one, therefor it is all over the place, but it can be fun reading. No solution. I have Asus motherboard Deluxe version, and they got rid od PS2 ports, so for me there was no other way but to reinstall OS. I was advised to disable the xHCI in the USB preferences on the BIOS, and check that the "Legacy USB" option is activated" It supposed to turn USB 3 to USB 2. I did not try it- I have try to put it on "Enabled" instead of "Smart Auto"- did not work. Also after I reinstalled OS, I did not have this problem. If you are on Asus, try to uninstall USB 3 boost- it came with the IA Suite on Asus motherboard disk. Right now I do not have that suite installed and I have no issues so far. http://answers.microsoft.com/en-us/windows/forum/windows8_1-system/usb-ports-failed-after-windows-81-update-can-not/8cb691a3-581d-4800-b70e-c09564e4aa26