I want to share my findings on playing this game in a window. Hopefully it will help new and returning players, so they don't get discouraged by the terrible fullscreen resolution.

1. Install DXWnd and run it.
2. Click "Edit" and then "Add". A new window will appear.
3. In the new window, in the "Path" textbox paste in the path to SC.exe in your game folder. In "Name" textbox type "Strategic Command" (or whatever you want).
4. In tab "Target" make sure that "Run in a Window" and "Do not notify on task switch" are turned ON.
5. In tab "Input" make sure that "Correct mouse position" is turned OFF.
6. Click "Ok" to save your changes.

"Do not notify on task switch" is to make sure that the game doesn't freeze after you unfocus from its window.
IMPORTANT: Do not unfocus from the game during AI turn. This almost always ends with a freeze. Just don't do it. It's annoying that you have to sit through AI turns, but I couldn't find a way around it.

"Correct mouse position" option was making my game continuously think the mouse was on the left edge of the screen, causing the map to keep scrolling to the left, making the game pretty much unplayable.

Sadly, I couldn't find a way to make it playable in a normal movable window. Maybe someone else will find some DXWnd options to make it work that way.