Why did my USB serial ports enumerate backward?

If you use a dual-boot system (Windows XP and Windows 2000), the COM ports may enumerate out of order after switching operating systems. This is because the device firmware is downloaded when the device is first powered. Because the firmware images for operation under Windows 2000 and Windows XP are different, and the USB bus power may not be cycled during a reboot, it is possible to run the incorrect firmware for the current operating system. You can fix this by disconnecting and reconnecting the USB-232 or USB-485 from the USB port or hub (and disconnecting power on the USB-485/4) to force the appropriate firmware to be downloaded.