I'm not too sure if you can play against other computer opponents-that's a good question.
I wondered the same thing as you, I wanted to know how my computer program would handle another computer program in chess.
So on my computer, this is what I did: On Chessmaster, I put it on computer VS human mode.
On the Fritz, I put it on human VS computer mode.
When it was the 'human's turn in Chessmaster, then I'll make sure the other Fritz made this move. Once Fritz moved, then I'll make the move in ChessMaster when it is the human's turn. Then it is ChessMaster's move. and etc etc...
I found it interesting how different computer programs play against each other...
I'm new here. I was wondering if one is allowed to play an old chess program here against other computer opponents. If not, that's fine but sometimes it is interesting to see how they do against other programs.