In this case, it's a CD or floppy disk that came with the monitor and which contains the monitor drivers. If you don't have one, you'll have to look for drivers on the monitor manufacturer's website.
Is this a common occurence that games won't recognize the monitor?
It's not that uncommon for games designed to only work in a fixed fullscreen resolution not to work with a widescreen monitor if you're using basic "Plug 'n Play" drivers.