I ran out of USB ports, so I went in for a powered USB hub. One by one, all the USB ports went out of action, and then windows (XP) would not boot normally. That was quite a scare. I detached all devices attached to the USB ports and ran Device Cleaner (thanks to Lookin) https://www.techspot.com/community/...up-and-remove-old-usb-storage-drivers.145884/ The PC began to boot normally, and all but one USB came alive. Any explanation?