Changing resolution, outside the game?

Okay, here's my problem:

When I try to play the game, the screen flashes several times then goes black. This is due to a monitor change, since I had the resolution at 1440x900 and now I'm using a smaller monitor (at my parent's house now).

So I tried running the game in windowed mode to get around this, but the windowed mode is still using 1440x900 I guess, since the mouse does nothing (the cursor changes to the game's, though).  So, is there an outside tool or document I can use to change the game's resolution? Short of buying a 1440x900 monitor, I can't find a way to fix this.

Help! I need to get my GalCiv2 fix.

I got hooked again and now this happens. It's torture.