1) Check the Bios for enabled USB ports.
2) Check Device Manager for disabled devices.
My USB ports are not working... I have a Dell Dimension 4550 desktop, running on Windows XP w/SP2. This system has a 2.6Ghz CPU and 256 RAM. When I try to use ANY USB device, my desktop does not see it... I move the USB devices to my other PC and the device works fine... however, not on this PC. When I have my USB mouse connected and boot the PC up... I see the light get activated on the mouse... then it goes off and the mouse does not work... and Windows (or the PC) does not see it. Please help.