Paul do you think David and myself among many others have not tried and failed, give in mate and listen to the voice of experience.
There is a hard way and an easy way, take the easy option and use a dedicated parallel port. Not pretty but functional.
Take the route that is proven to work.
Download a copy of linuxcnc and burn it to cd run as live cd, use the hdd for storage only any old pc with // will work. 1g ram is more than adequate for the job.
You'll be etching in minutes with the built in software.
I have a file of fonts and I mean a file of fonts, if you and David would like a copy I can upload them to somewhere later.