The devices you use...are they for USB1 format or 2 ?
Some usb devices need drivers loaded even on XP before they will work.
Do the following to check if there are no conflicts also :-
1)Right click my computer and select properties.
2)Select hardware tab and select device manager tab.
3)Click view (top of screen) and then click show hidden devices.
4)Click the plus signs next to every section on left of screen to expand the view and check for any item that is conflicting.
5)If you find any section with exclamation marks then this will be the reason. You can right click these and select properties again and it will usually tell you the reason for the conflict. This usually comes in the form that no drivers have been loaded.
Good Luck
Chris
November 2006