Many new drivers aren't signed by Microsoft so WinXP will warn you or even prevent you from installing new drivers for a device. To prevent this warning or to allow new un-signed drivers to be installed do the following:

1. Go to start/run/ then type secpol.msc
2. Browse to local policies/security options
3. Change "Devices: Unsigned driver installation behavior" setting to Silently succeed.
4. Reboot Computer.