As the originator of this thread a LONG time ago, I have been remiss in identifying my solution: Monaco font. It's monospaced (all characters are the same width) and the difference between the (slashed) zero and a capital "O" is very obvious. I use it with N1MM Logger. Here's a site you can download it from.http://www.gringod.com/wp-upload/MONACO.TTF
Once it's downloaded you have to install it in order for Windows to use it. In Win XP you do this via Control Panel/Fonts. From the screen that shows all your fonts, select File/Install New Font and then point to the folder that contains the downloaded file. Once that's done, test it by opening Microsoft Word and verify that you can select Monaco from the list of available fonts.