Want to play a CGA/EGA graphics game on a Win XP laptop

I have a laptop running Win XP and I have a copy of an old pc game which only runs on CGA or EGA graphics. The problem is I can't read the text unless I make the game think the screen is at CGA/EGA level. I've run the game before successfully, after using a Dos command to change the screen, but, now I can't remember what the command was. It's not a change I can make within the game, as I can't get into it in the first place. It's not working if I change the screen resolution under Desktop> Properties> Screen Resolution (even if I reboot). Any ideas? Thanks!