I just wasted a good many hours last night sweating over a hardware problem on my home desktop computer.
For no reason, my USB port went dead. It refused to acknowledge any peripheral that I tried to attach to it. My camera could not be detected, my thumbdrives could not be detected, my SD cards could not be detected.
I entered the Device Manager to see whether there was anything out of the ordinary there. Yes, under this Universal Serial Bus controller, there was an item saying "Unknown Device". Now, why did my USB port suddenly become an unknown device? I tried removing it but the computer kept adding it back again. My only hope then was to do a systematic disabling of some of the USB controllers one by one and then crossed my fingers. Yes, finally, after disabling this item -- the SiS PCI to USB Enhanced Host Controller -- the USB port sprang back to life.
I have a strange euphoria of achieving something but I still don't know the reason behind all this. Nevertheless, this simple solution worked for me.