The game is an old beast, and does not "auto-detect" anything on your computer. It can be rather finicky about your video settings. The game defaults to a 1024x768 mode, from Windows XP days.
It is usually best to set your Windows machine to match the "native" resolution of your LCD monitor, which Windows will refer to as "Recommended". ie: I am on my desktop, which has 2x 5:4 ratio NEC LCD 1850E displays, which have 1280x1024 resolution (yes, I are old). My laptop has a 17" screen that does 1600x900 (16:9 ratio) widescreen. In both cases, my video card is set to match those settings for the displays. Then, in the game under the Options menu, I have set the game to the same resolution, which fills the screen in both case, with a 5:4 ratio display on the desktop and a 16:9 ratio on the laptop. Works great.
You having two monitors, with the one being a laptop display, and the other an external monitor, might have to decide which way you're going to play, and leave things set at that. Else, just deal with having to change things each time you change displays, in that each time of starting the game, you're going to have to change the game's screen resolution to match the monitor. So you would start the game, change the resolution, and then re-start the game again for that to take effect. Or maybe do a batch file to start the game, and have that change the text file that holds that info prior to the start...
