How to: Add a Serial Port in Windows XP and 7 Guest.

[Mike_Iver_Village]

I don't feel this has been explained well at all

I have a USB multi serial port

On the Host, setup the hardware so it works in Device Manager

In VirtualBox
Enable USB
Do *Not* add any filters (these make the Guest try and setup the hardware *as well*)
In VirtualBox Serial Port setup, in the first COM port screen, set the upper COM as what you want the Guest *to see* (ie COM1)
Set the lower part of the screen select what the COM port actually is on the Host (it could be COM1, but in my case it was COM4)

That's it

[scottgus1]

In VirtualBox
Enable USB

This is not necessary. If the USB serial device is to be operated by the host, and only a serial port is to be passed into the VM, then USB is not necessary in the VM, only the serial port will be used. (Note that having USB enabled or disabled will not influence success or failure of the serial port being passed through. However, as you point out, setting up a USB filter for the USB device will pass the whole device into the VM and end-run around the serial settings. The VM could then run the serial ports directly, but the host could not use any of them. If you don't need the serial ports int he host OS, then using USB passthrough is an option to get serial ports into a VM.)