It's not specified how to create this .data file from the original game. It appears to be an unviewable png file, a format which didn't exist back when the game was released. The original game can be downloaded here:
No client is required for GamersGate, but you will need to run their installer to get at the files (works in WINE though last I checked). Sadly it's not on GOG yet.
http://www.gamersgate.com/DD-XCOMUD/x-com-ufo-defence
http://store.steampowered.com/app/7760/
No client is required for GamersGate, but you will need to run their installer to get at the files (works in WINE though last I checked). Sadly it's not on GOG yet.