And how do you get the platform number then?
Connect the camera to a Linux system, look to the number with lsusb, its part #2 of the USB device ID
(e.g. 04a9:318d for the SX10)Edit:
Also possible with Windows - you'll find the P-ID in the registry under the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB
(search for "Canon" / your camera model there), e.g. HardwareID = USB\Vid_04a9&Pid_318d&Rev_0002
for the SX10; the P-ID is also visible in the device manager tab, see attached image.