So when you plug the adapter into your XP machine, does it see that there is a device to install?
If so, go all the way through the install process to the point where XP can't find the software for the device, click finish, and then the more info link. In the page that comes back you should see a VID and a PID listed about halfway down. You must use these when editing the QTProg.inf file. XP can then tie the "software" to the device.
If not, check the device manager to see if it is hanging out in there waiting for drivers (you have to do this with it still plugged in). If you see it, remove the entry, unplug the device and try again.
Hope that helps...