It's possible to ignore all serial numbers, though this approach is NOT recommended. To ignore all serial numbers, in the above key, change this value to zero:
GlobalDisableSerNumGen = 1
To ignore the serial number for an individual device, create an entry under the above ...\UsbFlags key. The name must start with "IgnoreHWSerNum" followed by the vendor and product ID of the device. A value of 1 = "disable the serial number."