If you have the icon 'computer' on your desktop, right click it and click on properties then on hardware and finally on device manager. There will be an icon with a question mark, or poss a red cross if the usb controller is not working properly. You should be able to troubleshoot it from this menu.
You might also try going into the BIOS at startup [before windows loads]. Every comp is different but try continually pressing F1, F8 or Delete. Most comps show what buttons to press on the intial black screen. Once in there, see if there is a bit that refers to the USB controllers and make sure it says 'enabled' then press the key for 'save and exit' and it will boot up and all should be working.
I had the same problem when my old tower hadn't been connected to power for some time. Not one of the USB ports worked and the BIOS showed them as disabled, once corrected they were fine.
You might also need to restart the comp for this to take effect. If it still doesn't work, then you could search the net for an online driver, the device manager I mentioned should be able to do this.
jan c
January 2009
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Try fixfault.com to fix desktop pcs.