No USB devices detected in XP

I just built a brand new system for my client and clean-installed XP Home. USB support is enabled in the BIOS. In the Device Manager, USB support/hub entries are there. When I connect any USB device (mouse, ethernet, card reader) to either port, nothing happens. I have also run the Add Hardware Wizard, but it’s like it’s not even attached. The power light on the card reader comes on.