Start-->control panel-->system-->hardware tab-->device manager-->expand Universal Serial Bus Controllers-->right click and uninstall all of the USB root hubs-->restart-->they will reinstall on restart, and look for new hardware.
I thought I had a Hard Disk problem yesterday. I wasn't able to boot my PC, was stuck at the Dell loading screen.
I thought my PC wasn't detecting my HD anymore so I took out the HD, cleaned it a bit and put it back and it was all good.
But I just found out what was the real problem.
My PC can't boot if my headset is plugged. I just tried it a few times and every time my headset is still plugged, the PC won't boot and when I remove it, it all works fine.