Maybe, The camera may already be in your Device Manager but has
gone to Phantom or "Not Connected" status. Because of this when you
plug it back it - XP doesn't recognize it. This happens when you plug
a USB peripheral into a different socket.
Use Device Manager (w/ Camera unplugged), Click View, tic/check
"Show Hidden Devices". Expand the Digital Imaging category. If you
see your camera listed, but shown in diminished tone or grayed out
then Right Click the listing and choose Uninstall. Remove all instances
of the camera. Then re-insert your camera's USB plug.