Preventing USB devices with different serials to be seen as separate devices

Once again, I have to give props to Xiaofan:

The following is quoted from a USB-IF forum post (the link is now invalid)
http://www.usb.org/phpbb/viewtopic.php?p=33850

"Win2000/XP has a way to ignore the serial number.
This is copied form an AppNote I wrote:
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Ignore serial number in Win2000 / XP In Windows 2000 and XP,
there is a way to ignore the serial number for a certain device.
This is not recommended in general, but there are reasons to do so.

This is the registry key
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\UsbFlags]
The global way: The entry below does enable the serial numbers despite
its name! It is already there after a fresh installation.
GlobalDisableSerNumGen = 1
We recommend keeping the above setting unchanged.

Now here is the individual way. Create an entry under the
above ...\UsbFlags key. The name must start with "IgnoreHWSerNum"
followed by the vendor and product ID of the device. The value for the
entry is 1 for disable.
Example:
IgnoreHWSerNum0536016A= 1
Our vendor ID (VID) is 0536 (hex), the product ID (PID) depends
on the interface you choose.