In My Computer/Properties, select the Advanced Tab, then select Environment Variables, select New. In the New User Variable box, Variable name: devmgr_show_nonpresent_devices
Variable value: 1
Click on the OK button.
Go to Device Manager, select View, then select "Show hidden devices."
You should now see all your present and non-present devices, including your USB devices and hubs and ports. Now uninstall all the USB non-present devices. Re-start your computer. After XP loads, it will find and install any USB devices (e.g., keyboard and mouse) plugged in the computer. Now try your USB stick and your USB HDD.