do you have exclamation or question marks at the device manager?

Okay! What is the make and model of your pc. Be specific.

Update BIOS and drivers for chipset if you don't have the newest versions .If you have already the newest BIOS & drivers or updating don't help follow below:

Two methods to fix

1.from this MS article:Advanced troubleshooting tips for general USB problems in Windows XP

Remove and reinstall all USB controllers

To remove and reinstall all USB controllers, follow these steps:

1. Click Start, click Run, type sysdm.cpl in the Open box, and then click OK.
2. Click the Hardware tab.
3. Click the Device Manager button.
4. Expand Universal Serial Bus controllers.
5. Right-click every device under the Universal Serial Bus controllers node, and then click Uninstall to remove them one at a time.
6. Restart the computer, and then reinstall the USB controllers.
7. Plug in the removable USB storage device, and then test to make sure that the issue is resolved.

2.

1.Extract from DVD (the best way use 7-zip or WinRAR to dothat) these files:

from X:\Windows\inf

usb.inf
usbccid.inf
usbcir.inf
usbport.inf
usbprint.inf
usbstor.inf
usbvideo.inf

from X:\Windows\System32

usbmon.dll
usbperf.dll
usbui.dll

and place all extracted Inf file in C:\Windows\inf and all dll modules C:\Windows\System32 (replace the old ones)
2.In device manager open USB controllers and remove each one device -don't restart computer untill remove all devices in USB controllers!
3.When you remove all USB Controllers devices you can now restart computer.