Can we change literally any aspect?

[Dart]

I know this game is as old as they come, but is there now way AT ALL to change the resolution of windowed mode? Or is it ancient 1990s reso or full screen only?

[aable14all]

You have to edit one of the *.ini files. I cannot remember which one, but it can be done.

[Empiro]

You can edit DosBox.conf to set the resolution. Note that you'll also need to change the render method from "Surface" to "ddraw".

Also, you can try checking out OpenXCom, which is basically an open source clone (you still need X-Com from Steam or elsewhere):
http://openxcom.org/

[duanevp]

The resolution is hard-coded into the game. It was created in 1994 when it was something of a pie-in-the-sky dream to have graphics better than 800x600 on your desktop and it most certainly wasn't created to EVER be moddable. Openxcom has the potential for a higher resolution mod but because the original game has only ONE resolution for its graphics it means individually redrawing every pixel of graphics in the game to actually have a different (better) resolution. I believe there's one guy who's working on that but it's a huge undertaking and isn't something that openxcom is really considering at the moment as I understand.

Xcom (and still with openxcom, IIUC) uses its graphics in really odd and unexpected ways because it was written JUST to do what it does, not act as a game engine into which you could plug alterations or improvements, so it gets wierd as to what the game well let you see, what it considers as a solid wall or object, how other things interact with them etc. For example, how it handles the "back" walls of UFO's is different from other walls and presents problems if you try to put a doorway into a back wall.

You can make the game WINDOW itself larger or smaller but the actual resolution of the graphics is one-size-fits-all.

[Incunabulum]

Open XCOM. You've already got the game so get the version that fixes the remaining bugs *and* allows you the resolution you want. Along with adding some decent new options - like smoothing out the pixelization so the game doesn't look 20 years old (and horrible in HD) and not having to re-equip each individual soldier every. damn. mission.