You should take a look at JoyToKey:
http://www.electracode.com/4/joy2key/JoyToKey%20English%20Version.htm ; it' s an awesome tool (freeware) that lets you assign keyboard presses (and even mouse buttons) to the buttons of your joypad. With this you can make just about any game joypad-compatible.
I' ve just tested it with the original DOS version of Raptor and it works like a charm. Should also work perfectly with the Gog.com version of Raptor. Have fun!
porphiron: anyone had any luck getting this sucker to work, so far no dice?
i wanna play this game, i bought he bloody shareware version years ago, in fact i still have the disk....