I'm running the game on an old square monitor, not widescreen. Every setting under the Graphics Mode Setup results in the center of the main menu being askew, to the right side of the screen, and my pointer can go off the screen to the right. One time I tried alt-tabbing and got it to run in a window, but then it randomly crashed on me.

Any suggestions to get the resolution fixed, aside from go buy a widescreen monitor? =)

use your monitor controls to center the picture right ?
Your monitor probably has never been configured for that resolution.

Alternatively press alt-enter to play in a window

It's not just that the screen was off-centered; it was stretched, and it went off the screen to the right.

I didn't know about the Alt-Enter method, but I can try it if needed.

I simply went into the CONF file and set the default resolution to 800x600. That cleared things up fine.