So, followed this thread

re the Huanyang VFD control plugin for Mach3, USB RS-485

bought the recommended usb gizmo from here

USB to RS485 USB-485 Converter Adapter Support Win7 XP Vista Linux Mac UK seller | eBay

downloaded the driver from 2303 prolific driver as recommended in the thread

installed it

plugged in usb gizmo, im rolling with windows xp

just get Click image for larger version. 

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tried to manually install the driver, but cant find where the useful prolific setup package puts the inf or where it unpacks to etc

can anybody help?