DeathStrike: Well, this DOS version is the only actual DOS version. The original version is the Apple II version from 1980. They are functionally the same game.
Actually, there are a few minor differences between the original and the remake, and one significant one. The significant one is that the Apple original didn't have wandering monsters on the main world map. The only combat was in the dungeons, and of course against Mondain at the end. The minor differences included variant town/castle maps and resurrection of dead characters (in the original game death was permanent).
Just remember that Ultima 2, 3, 4 and 5 have upgrade patches to effectively make them the best versions, while Ultima 1 never needed one because it was released in 1986 as my previous post mentions.
There
is a patch for the DOS
Ultima I, however, that corrects a slight graphical bug: Text can sometimes glitch out when encountering enemies with long names. It's not a show-stopper, however.