I just bought a brand new internal 3.5 inch card reader with one USB 2.0 port and all you are supposed to do is connect it to your internal USB header (which I did) and when I powered on my computer the power light comes on on the card reader but nothing happens if I connect a mouse or other USB device the system will not notice it I have XP if that helps any
Check the properties of the USB Root Hub in the Device Manager. There is a power management feature in xp that turns the USB off to save power.
A card reader should not need drivers to work with Windows XP. You would only need drivers if you were using Windows 98 or earlier. All I can think of is that you haven't connected it to the header correctly; or maybe you've got the connector the wrong way round. Or maybe the header is faulty (if you have another USB header on your motherboard that has something plugged into it, perhaps you could try swapping them over).